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 $168.40   13.271%   $190.7484   $190.75   $190.75   $190.70  
  Purchase #2 $45.49   9.408%   $49.7697   $49.77   $49.75   $49.80  
  Purchase #3 $186.36   7.292%   $199.9494   $199.95   $199.95   $199.90  
  Purchase #4 $62.27   7.112%   $66.6986   $66.70   $66.70   $66.70  
  Purchase #5 $73.25   12.315%   $82.2707   $82.27   $82.25   $82.30  
  Purchase #6 $44.77   8.527%   $48.5875   $48.59   $48.60   $48.60  
  Purchase #7 $82.29   6.211%   $87.401   $87.40   $87.40   $87.40  
  7 purchase totals = $662.83       $725.4253   $725.43   $725.40   $725.40