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 $46.51   13.134%   $52.6186   $52.62   $52.60   $52.60  
  Purchase #2 $129.94   8.260%   $140.673   $140.67   $140.65   $140.70  
  Purchase #3 $199.31   9.387%   $218.0192   $218.02   $218.00   $218.00  
  Purchase #4 $244.53   12.766%   $275.7467   $275.75   $275.75   $275.70  
  Purchase #5 $100.82   11.849%   $112.7662   $112.77   $112.75   $112.80  
  Purchase #6 $248.67   9.344%   $271.9057   $271.91   $271.90   $271.90  
  Purchase #7 $193.64   4.300%   $201.9665   $201.97   $201.95   $202.00  
  7 purchase totals = $1,163.42       $1,273.6959   $1,273.71   $1,273.60   $1,273.70