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 $216.49   8.362%   $234.5929   $234.59   $234.60   $234.60  
  Purchase #2 $71.51   6.449%   $76.1217   $76.12   $76.10   $76.10  
  Purchase #3 $195.76   3.610%   $202.8269   $202.83   $202.85   $202.80  
  Purchase #4 $21.31   13.282%   $24.1404   $24.14   $24.15   $24.10  
  Purchase #5 $71.43   9.539%   $78.2437   $78.24   $78.25   $78.20  
  Purchase #6 $54.47   7.617%   $58.619   $58.62   $58.60   $58.60  
  Purchase #7 $179.29   4.726%   $187.7632   $187.76   $187.75   $187.80  
  7 purchase totals = $810.26       $862.3078   $862.30   $862.30   $862.20