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 $91.61   4.501%   $95.7334   $95.73   $95.75   $95.70  
  Purchase #2 $49.86   11.521%   $55.6044   $55.60   $55.60   $55.60  
  Purchase #3 $46.27   5.589%   $48.856   $48.86   $48.85   $48.90  
  Purchase #4 $21.29   9.748%   $23.3653   $23.37   $23.35   $23.40  
  Purchase #5 $190.62   8.210%   $206.2699   $206.27   $206.25   $206.30  
  Purchase #6 $162.40   13.254%   $183.9245   $183.92   $183.90   $183.90  
  Purchase #7 $133.51   12.810%   $150.6126   $150.61   $150.60   $150.60  
  7 purchase totals = $695.56       $764.3661   $764.36   $764.30   $764.40