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 $56.29   11.834%   $62.9514   $62.95   $62.95   $63.00  
  Purchase #2 $111.71   4.669%   $116.9257   $116.93   $116.95   $116.90  
  Purchase #3 $64.64   6.801%   $69.0362   $69.04   $69.05   $69.00  
  Purchase #4 $156.85   4.202%   $163.4408   $163.44   $163.45   $163.40  
  Purchase #5 $116.44   7.409%   $125.067   $125.07   $125.05   $125.10  
  Purchase #6 $214.78   10.780%   $237.9333   $237.93   $237.95   $237.90  
  Purchase #7 $149.82   6.108%   $158.971   $158.97   $158.95   $159.00  
  7 purchase totals = $870.53       $934.3254   $934.33   $934.35   $934.30