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 $228.53   7.189%   $244.959   $244.96   $244.95   $245.00  
  Purchase #2 $234.74   9.140%   $256.1952   $256.20   $256.20   $256.20  
  Purchase #3 $45.59   8.190%   $49.3238   $49.32   $49.30   $49.30  
  Purchase #4 $226.55   12.516%   $254.905   $254.91   $254.90   $254.90  
  Purchase #5 $209.74   3.686%   $217.471   $217.47   $217.45   $217.50  
  Purchase #6 $228.58   11.657%   $255.2256   $255.23   $255.25   $255.20  
  Purchase #7 $190.99   10.383%   $210.8205   $210.82   $210.80   $210.80  
  7 purchase totals = $1,364.72       $1,488.9001   $1,488.91   $1,488.85   $1,488.90