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 $105.94   8.432%   $114.8729   $114.87   $114.85   $114.90  
  Purchase #2 $186.46   3.582%   $193.139   $193.14   $193.15   $193.10  
  Purchase #3 $12.46   10.639%   $13.7856   $13.79   $13.80   $13.80  
  Purchase #4 $59.27   10.674%   $65.5965   $65.60   $65.60   $65.60  
  Purchase #5 $99.51   4.676%   $104.1631   $104.16   $104.15   $104.20  
  Purchase #6 $88.61   10.510%   $97.9229   $97.92   $97.90   $97.90  
  Purchase #7 $160.83   6.205%   $170.8095   $170.81   $170.80   $170.80  
  7 purchase totals = $713.08       $760.2895   $760.29   $760.25   $760.30