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 $69.37   3.160%   $71.5621   $71.56   $71.55   $71.60  
  Purchase #2 $182.50   7.797%   $196.7295   $196.73   $196.75   $196.70  
  Purchase #3 $240.66   5.607%   $254.1538   $254.15   $254.15   $254.20  
  Purchase #4 $102.40   9.354%   $111.9785   $111.98   $112.00   $112.00  
  Purchase #5 $242.73   13.163%   $274.6805   $274.68   $274.70   $274.70  
  Purchase #6 $226.73   3.187%   $233.9559   $233.96   $233.95   $234.00  
  Purchase #7 $167.34   8.670%   $181.8484   $181.85   $181.85   $181.80  
  7 purchase totals = $1,231.73       $1,324.9087   $1,324.91   $1,324.95   $1,325.00