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 $119.25   3.733%   $123.7016   $123.70   $123.70   $123.70  
  Purchase #2 $218.85   4.751%   $229.2476   $229.25   $229.25   $229.20  
  Purchase #3 $202.43   11.475%   $225.6588   $225.66   $225.65   $225.70  
  Purchase #4 $236.48   5.462%   $249.3965   $249.40   $249.40   $249.40  
  Purchase #5 $111.45   7.510%   $119.8199   $119.82   $119.80   $119.80  
  Purchase #6 $64.29   6.240%   $68.3017   $68.30   $68.30   $68.30  
  Purchase #7 $69.41   9.663%   $76.1171   $76.12   $76.10   $76.10  
  7 purchase totals = $1,022.16       $1,092.2432   $1,092.25   $1,092.20   $1,092.20