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 $60.55   4.478%   $63.2614   $63.26   $63.25   $63.30  
  Purchase #2 $173.33   7.301%   $185.9848   $185.98   $186.00   $186.00  
  Purchase #3 $79.54   7.567%   $85.5588   $85.56   $85.55   $85.60  
  Purchase #4 $85.27   12.255%   $95.7198   $95.72   $95.70   $95.70  
  Purchase #5 $90.95   6.847%   $97.1773   $97.18   $97.20   $97.20  
  Purchase #6 $61.41   12.223%   $68.9161   $68.92   $68.90   $68.90  
  Purchase #7 $119.51   5.769%   $126.4045   $126.40   $126.40   $126.40  
  7 purchase totals = $670.56       $723.0227   $723.02   $723.00   $723.10