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 $248.51   4.680%   $260.1403   $260.14   $260.15   $260.10  
  Purchase #2 $19.78   7.171%   $21.1984   $21.20   $21.20   $21.20  
  Purchase #3 $168.87   8.844%   $183.8049   $183.80   $183.80   $183.80  
  Purchase #4 $157.34   3.299%   $162.5306   $162.53   $162.55   $162.50  
  Purchase #5 $231.47   8.501%   $251.1473   $251.15   $251.15   $251.10  
  Purchase #6 $107.55   12.382%   $120.8668   $120.87   $120.85   $120.90  
  Purchase #7 $162.37   3.381%   $167.8597   $167.86   $167.85   $167.90  
  7 purchase totals = $1,095.89       $1,167.5480   $1,167.55   $1,167.55   $1,167.50