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 $62.95   11.128%   $69.9551   $69.96   $69.95   $70.00  
  Purchase #2 $236.37   5.816%   $250.1173   $250.12   $250.10   $250.10  
  Purchase #3 $11.70   6.182%   $12.4233   $12.42   $12.40   $12.40  
  Purchase #4 $46.44   6.273%   $49.3532   $49.35   $49.35   $49.40  
  Purchase #5 $100.63   10.480%   $111.176   $111.18   $111.20   $111.20  
  Purchase #6 $130.60   7.732%   $140.698   $140.70   $140.70   $140.70  
  Purchase #7 $166.26   4.166%   $173.1864   $173.19   $173.20   $173.20  
  7 purchase totals = $754.95       $806.9093   $806.92   $806.90   $807.00