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 $86.63   6.293%   $92.0816   $92.08   $92.10   $92.10  
  Purchase #2 $168.88   4.205%   $175.9814   $175.98   $176.00   $176.00  
  Purchase #3 $53.39   4.359%   $55.7173   $55.72   $55.70   $55.70  
  Purchase #4 $110.58   10.380%   $122.0582   $122.06   $122.05   $122.10  
  Purchase #5 $46.48   13.266%   $52.646   $52.65   $52.65   $52.60  
  Purchase #6 $163.36   4.661%   $170.9742   $170.97   $170.95   $171.00  
  Purchase #7 $69.46   11.552%   $77.484   $77.48   $77.50   $77.50  
  7 purchase totals = $698.78       $746.9427   $746.94   $746.95   $747.00