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 $83.59   13.193%   $94.618   $94.62   $94.60   $94.60  
  Purchase #2 $47.81   8.157%   $51.7099   $51.71   $51.70   $51.70  
  Purchase #3 $13.56   11.457%   $15.1136   $15.11   $15.10   $15.10  
  Purchase #4 $77.67   9.323%   $84.9112   $84.91   $84.90   $84.90  
  Purchase #5 $188.59   4.812%   $197.665   $197.67   $197.65   $197.70  
  Purchase #6 $210.90   9.473%   $230.8786   $230.88   $230.90   $230.90  
  Purchase #7 $47.39   12.350%   $53.2427   $53.24   $53.25   $53.20  
  7 purchase totals = $669.51       $728.1390   $728.14   $728.10   $728.10