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 $44.62   3.469%   $46.1679   $46.17   $46.15   $46.20  
  Purchase #2 $45.98   7.307%   $49.3398   $49.34   $49.35   $49.30  
  Purchase #3 $195.84   6.580%   $208.7263   $208.73   $208.75   $208.70  
  Purchase #4 $101.95   7.206%   $109.2965   $109.30   $109.30   $109.30  
  Purchase #5 $240.64   9.447%   $263.3733   $263.37   $263.35   $263.40  
  Purchase #6 $245.73   7.599%   $264.403   $264.40   $264.40   $264.40  
  Purchase #7 $88.86   8.198%   $96.1447   $96.14   $96.15   $96.10  
  7 purchase totals = $963.62       $1,037.4515   $1,037.45   $1,037.45   $1,037.40