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 $114.49   9.816%   $125.7283   $125.73   $125.75   $125.70  
  Purchase #2 $112.32   10.356%   $123.9519   $123.95   $123.95   $124.00  
  Purchase #3 $88.73   3.834%   $92.1319   $92.13   $92.15   $92.10  
  Purchase #4 $164.87   7.748%   $177.6441   $177.64   $177.65   $177.60  
  Purchase #5 $78.94   3.347%   $81.5821   $81.58   $81.60   $81.60  
  Purchase #6 $248.52   13.268%   $281.4936   $281.49   $281.50   $281.50  
  Purchase #7 $190.26   7.375%   $204.2917   $204.29   $204.30   $204.30  
  7 purchase totals = $998.13       $1,086.8236   $1,086.81   $1,086.90   $1,086.80