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 $226.73   7.638%   $244.0476   $244.05   $244.05   $244.00  
  Purchase #2 $24.85   9.556%   $27.2247   $27.22   $27.20   $27.20  
  Purchase #3 $88.66   10.863%   $98.2911   $98.29   $98.30   $98.30  
  Purchase #4 $159.44   5.162%   $167.6703   $167.67   $167.65   $167.70  
  Purchase #5 $64.28   8.696%   $69.8698   $69.87   $69.85   $69.90  
  Purchase #6 $106.37   6.368%   $113.1436   $113.14   $113.15   $113.10  
  Purchase #7 $141.73   4.762%   $148.4792   $148.48   $148.50   $148.50  
  7 purchase totals = $812.06       $868.7263   $868.72   $868.70   $868.70