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 $118.41   6.255%   $125.8165   $125.82   $125.80   $125.80  
  Purchase #2 $125.45   5.518%   $132.3723   $132.37   $132.35   $132.40  
  Purchase #3 $44.36   13.866%   $50.511   $50.51   $50.50   $50.50  
  Purchase #4 $87.88   3.519%   $90.9725   $90.97   $90.95   $91.00  
  Purchase #5 $236.43   9.673%   $259.2999   $259.30   $259.30   $259.30  
  Purchase #6 $164.81   10.501%   $182.1167   $182.12   $182.10   $182.10  
  Purchase #7 $153.32   12.368%   $172.2826   $172.28   $172.30   $172.30  
  7 purchase totals = $930.66       $1,013.3715   $1,013.37   $1,013.30   $1,013.40