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 $161.87   4.376%   $168.9534   $168.95   $168.95   $169.00  
  Purchase #2 $54.50   3.744%   $56.5405   $56.54   $56.55   $56.50  
  Purchase #3 $111.92   12.283%   $125.6671   $125.67   $125.65   $125.70  
  Purchase #4 $216.29   13.429%   $245.3356   $245.34   $245.35   $245.30  
  Purchase #5 $221.66   12.268%   $248.8532   $248.85   $248.85   $248.90  
  Purchase #6 $136.65   12.308%   $153.4689   $153.47   $153.45   $153.50  
  Purchase #7 $65.28   4.422%   $68.1667   $68.17   $68.15   $68.20  
  7 purchase totals = $968.17       $1,066.9854   $1,066.99   $1,066.95   $1,067.10