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 $147.63   6.355%   $157.0119   $157.01   $157.00   $157.00  
  Purchase #2 $169.48   9.363%   $185.3484   $185.35   $185.35   $185.30  
  Purchase #3 $25.94   6.523%   $27.6321   $27.63   $27.65   $27.60  
  Purchase #4 $146.62   9.257%   $160.1926   $160.19   $160.20   $160.20  
  Purchase #5 $160.90   9.146%   $175.6159   $175.62   $175.60   $175.60  
  Purchase #6 $101.81   8.782%   $110.751   $110.75   $110.75   $110.80  
  Purchase #7 $130.90   3.352%   $135.2878   $135.29   $135.30   $135.30  
  7 purchase totals = $883.28       $951.8397   $951.84   $951.85   $951.80