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 $40.95   5.733%   $43.2977   $43.30   $43.30   $43.30  
  Purchase #2 $111.65   4.675%   $116.8696   $116.87   $116.85   $116.90  
  Purchase #3 $175.61   7.385%   $188.5788   $188.58   $188.60   $188.60  
  Purchase #4 $184.92   6.844%   $197.5759   $197.58   $197.60   $197.60  
  Purchase #5 $66.26   4.477%   $69.2265   $69.23   $69.25   $69.20  
  Purchase #6 $153.43   13.216%   $173.7073   $173.71   $173.70   $173.70  
  Purchase #7 $153.61   4.398%   $160.3658   $160.37   $160.35   $160.40  
  7 purchase totals = $886.43       $949.6216   $949.64   $949.65   $949.70