Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $106.44   6.326%   $113.1734   $113.17   $113.15   $113.20  
  Purchase #2 $226.31   11.795%   $253.0033   $253.00   $253.00   $253.00  
  Purchase #3 $151.25   12.451%   $170.0821   $170.08   $170.10   $170.10  
  Purchase #4 $224.43   13.874%   $255.5674   $255.57   $255.55   $255.60  
  Purchase #5 $210.64   8.714%   $228.9952   $229.00   $229.00   $229.00  
  Purchase #6 $184.98   13.849%   $210.5979   $210.60   $210.60   $210.60  
  Purchase #7 $211.99   13.412%   $240.4221   $240.42   $240.40   $240.40  
  7 purchase totals = $1,316.04       $1,471.8414   $1,471.84   $1,471.80   $1,471.90