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 $126.61   4.389%   $132.1669   $132.17   $132.15   $132.20  
  Purchase #2 $128.30   10.390%   $141.6304   $141.63   $141.65   $141.60  
  Purchase #3 $163.96   10.161%   $180.62   $180.62   $180.60   $180.60  
  Purchase #4 $171.89   9.222%   $187.7417   $187.74   $187.75   $187.70  
  Purchase #5 $145.31   11.589%   $162.15   $162.15   $162.15   $162.20  
  Purchase #6 $57.71   7.315%   $61.9315   $61.93   $61.95   $61.90  
  Purchase #7 $190.50   3.743%   $197.6304   $197.63   $197.65   $197.60  
  7 purchase totals = $984.28       $1,063.8709   $1,063.87   $1,063.90   $1,063.80