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 $86.62   10.761%   $95.9412   $95.94   $95.95   $95.90  
  Purchase #2 $146.38   3.291%   $151.1974   $151.20   $151.20   $151.20  
  Purchase #3 $21.63   10.736%   $23.9522   $23.95   $23.95   $24.00  
  Purchase #4 $150.31   5.868%   $159.1302   $159.13   $159.15   $159.10  
  Purchase #5 $146.52   6.725%   $156.3735   $156.37   $156.35   $156.40  
  Purchase #6 $87.54   5.562%   $92.409   $92.41   $92.40   $92.40  
  Purchase #7 $250.89   9.399%   $274.4712   $274.47   $274.45   $274.50  
  7 purchase totals = $889.89       $953.4747   $953.47   $953.45   $953.50