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 $41.92   10.323%   $46.2474   $46.25   $46.25   $46.20  
  Purchase #2 $140.66   9.682%   $154.2787   $154.28   $154.30   $154.30  
  Purchase #3 $124.66   3.227%   $128.6828   $128.68   $128.70   $128.70  
  Purchase #4 $73.29   11.725%   $81.8833   $81.88   $81.90   $81.90  
  Purchase #5 $52.65   13.857%   $59.9457   $59.95   $59.95   $59.90  
  Purchase #6 $211.65   5.571%   $223.441   $223.44   $223.45   $223.40  
  Purchase #7 $216.70   6.872%   $231.5916   $231.59   $231.60   $231.60  
  7 purchase totals = $861.53       $926.0705   $926.07   $926.15   $926.00