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 $59.97   3.402%   $62.0102   $62.01   $62.00   $62.00  
  Purchase #2 $25.47   8.732%   $27.694   $27.69   $27.70   $27.70  
  Purchase #3 $6.47   7.651%   $6.965   $6.97   $6.95   $7.00  
  Purchase #4 $187.51   6.535%   $199.7638   $199.76   $199.75   $199.80  
  Purchase #5 $151.42   8.388%   $164.1211   $164.12   $164.10   $164.10  
  Purchase #6 $186.71   10.192%   $205.7395   $205.74   $205.75   $205.70  
  Purchase #7 $106.95   8.557%   $116.1017   $116.10   $116.10   $116.10  
  7 purchase totals = $724.50       $782.3953   $782.39   $782.35   $782.40