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 $244.44   7.261%   $262.1888   $262.19   $262.20   $262.20  
  Purchase #2 $149.46   8.234%   $161.7665   $161.77   $161.75   $161.80  
  Purchase #3 $54.83   7.140%   $58.7449   $58.74   $58.75   $58.70  
  Purchase #4 $224.52   8.298%   $243.1507   $243.15   $243.15   $243.20  
  Purchase #5 $32.75   12.313%   $36.7825   $36.78   $36.80   $36.80  
  Purchase #6 $213.57   6.545%   $227.5482   $227.55   $227.55   $227.50  
  Purchase #7 $55.63   4.620%   $58.2001   $58.20   $58.20   $58.20  
  7 purchase totals = $975.20       $1,048.3817   $1,048.38   $1,048.40   $1,048.40