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 $117.98   6.824%   $126.031   $126.03   $126.05   $126.00  
  Purchase #2 $152.51   5.350%   $160.6693   $160.67   $160.65   $160.70  
  Purchase #3 $173.32   3.154%   $178.7865   $178.79   $178.80   $178.80  
  Purchase #4 $156.37   10.585%   $172.9218   $172.92   $172.90   $172.90  
  Purchase #5 $249.47   6.763%   $266.3417   $266.34   $266.35   $266.30  
  Purchase #6 $159.38   6.787%   $170.1971   $170.20   $170.20   $170.20  
  Purchase #7 $192.64   8.856%   $209.7002   $209.70   $209.70   $209.70  
  7 purchase totals = $1,201.67       $1,284.6476   $1,284.65   $1,284.65   $1,284.60