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 $95.45   6.794%   $101.9349   $101.93   $101.95   $101.90  
  Purchase #2 $132.38   8.136%   $143.1504   $143.15   $143.15   $143.20  
  Purchase #3 $78.67   7.738%   $84.7575   $84.76   $84.75   $84.80  
  Purchase #4 $126.36   5.171%   $132.8941   $132.89   $132.90   $132.90  
  Purchase #5 $156.35   11.701%   $174.6445   $174.64   $174.65   $174.60  
  Purchase #6 $152.39   9.583%   $166.9935   $166.99   $167.00   $167.00  
  Purchase #7 $16.68   5.821%   $17.6509   $17.65   $17.65   $17.70  
  7 purchase totals = $758.28       $822.0258   $822.01   $822.05   $822.10