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 $84.87   12.439%   $95.427   $95.43   $95.45   $95.40  
  Purchase #2 $158.51   5.373%   $167.0267   $167.03   $167.05   $167.00  
  Purchase #3 $88.33   6.238%   $93.84   $93.84   $93.85   $93.80  
  Purchase #4 $78.76   5.356%   $82.9784   $82.98   $83.00   $83.00  
  Purchase #5 $214.39   11.335%   $238.6911   $238.69   $238.70   $238.70  
  Purchase #6 $13.87   9.177%   $15.1428   $15.14   $15.15   $15.10  
  Purchase #7 $226.61   9.513%   $248.1674   $248.17   $248.15   $248.20  
  7 purchase totals = $865.34       $941.2734   $941.28   $941.35   $941.20