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 $202.86   5.421%   $213.857   $213.86   $213.85   $213.90  
  Purchase #2 $120.82   4.784%   $126.6   $126.60   $126.60   $126.60  
  Purchase #3 $55.36   12.314%   $62.177   $62.18   $62.20   $62.20  
  Purchase #4 $110.31   8.418%   $119.5959   $119.60   $119.60   $119.60  
  Purchase #5 $47.63   3.609%   $49.349   $49.35   $49.35   $49.30  
  Purchase #6 $18.61   12.283%   $20.8959   $20.90   $20.90   $20.90  
  Purchase #7 $169.95   12.643%   $191.4368   $191.44   $191.45   $191.40  
  7 purchase totals = $725.54       $783.9116   $783.93   $783.95   $783.90