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 $86.94   10.576%   $96.1348   $96.13   $96.15   $96.10  
  Purchase #2 $241.92   7.794%   $260.7752   $260.78   $260.80   $260.80  
  Purchase #3 $194.42   3.179%   $200.6006   $200.60   $200.60   $200.60  
  Purchase #4 $168.31   11.707%   $188.0141   $188.01   $188.00   $188.00  
  Purchase #5 $88.40   13.421%   $100.2642   $100.26   $100.25   $100.30  
  Purchase #6 $210.62   8.412%   $228.3374   $228.34   $228.35   $228.30  
  Purchase #7 $141.37   8.175%   $152.927   $152.93   $152.95   $152.90  
  7 purchase totals = $1,131.98       $1,227.0533   $1,227.05   $1,227.10   $1,227.00