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 $55.98   8.414%   $60.6902   $60.69   $60.70   $60.70  
  Purchase #2 $212.25   10.676%   $234.9098   $234.91   $234.90   $234.90  
  Purchase #3 $73.94   4.750%   $77.4522   $77.45   $77.45   $77.50  
  Purchase #4 $178.29   12.488%   $200.5549   $200.55   $200.55   $200.60  
  Purchase #5 $193.25   7.134%   $207.0365   $207.04   $207.05   $207.00  
  Purchase #6 $49.90   11.265%   $55.5212   $55.52   $55.50   $55.50  
  Purchase #7 $236.43   9.764%   $259.515   $259.52   $259.50   $259.50  
  7 purchase totals = $1,000.04       $1,095.6798   $1,095.68   $1,095.65   $1,095.70