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 $63.88   13.693%   $72.6271   $72.63   $72.65   $72.60  
  Purchase #2 $184.64   5.273%   $194.3761   $194.38   $194.40   $194.40  
  Purchase #3 $177.87   5.484%   $187.6244   $187.62   $187.60   $187.60  
  Purchase #4 $149.52   7.411%   $160.6009   $160.60   $160.60   $160.60  
  Purchase #5 $56.61   7.803%   $61.0273   $61.03   $61.05   $61.00  
  Purchase #6 $139.53   11.317%   $155.3206   $155.32   $155.30   $155.30  
  Purchase #7 $90.28   4.504%   $94.3462   $94.35   $94.35   $94.30  
  7 purchase totals = $862.33       $925.9226   $925.93   $925.95   $925.80