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 $176.42   11.579%   $196.8477   $196.85   $196.85   $196.80  
  Purchase #2 $140.96   9.372%   $154.1708   $154.17   $154.15   $154.20  
  Purchase #3 $101.61   5.557%   $107.2565   $107.26   $107.25   $107.30  
  Purchase #4 $63.62   3.830%   $66.0566   $66.06   $66.05   $66.10  
  Purchase #5 $54.63   5.870%   $57.8368   $57.84   $57.85   $57.80  
  Purchase #6 $6.64   9.862%   $7.2948   $7.29   $7.30   $7.30  
  Purchase #7 $149.59   9.221%   $163.3837   $163.38   $163.40   $163.40  
  7 purchase totals = $693.47       $752.8469   $752.85   $752.85   $752.90