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 $84.46   13.356%   $95.7405   $95.74   $95.75   $95.70  
  Purchase #2 $22.78   3.163%   $23.5005   $23.50   $23.50   $23.50  
  Purchase #3 $101.56   5.740%   $107.3895   $107.39   $107.40   $107.40  
  Purchase #4 $206.60   8.513%   $224.1879   $224.19   $224.20   $224.20  
  Purchase #5 $147.76   3.598%   $153.0764   $153.08   $153.10   $153.10  
  Purchase #6 $176.80   10.461%   $195.295   $195.30   $195.30   $195.30  
  Purchase #7 $62.84   5.849%   $66.5155   $66.52   $66.50   $66.50  
  7 purchase totals = $802.80       $865.7053   $865.72   $865.75   $865.70