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 $129.95   9.422%   $142.1939   $142.19   $142.20   $142.20  
  Purchase #2 $167.38   3.718%   $173.6032   $173.60   $173.60   $173.60  
  Purchase #3 $195.36   10.402%   $215.6813   $215.68   $215.70   $215.70  
  Purchase #4 $53.80   3.417%   $55.6383   $55.64   $55.65   $55.60  
  Purchase #5 $89.49   10.130%   $98.5553   $98.56   $98.55   $98.60  
  Purchase #6 $182.35   3.227%   $188.2344   $188.23   $188.25   $188.20  
  Purchase #7 $133.28   13.237%   $150.9223   $150.92   $150.90   $150.90  
  7 purchase totals = $951.61       $1,024.8287   $1,024.82   $1,024.85   $1,024.80