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 $62.81   3.466%   $64.987   $64.99   $65.00   $65.00  
  Purchase #2 $187.89   5.599%   $198.41   $198.41   $198.40   $198.40  
  Purchase #3 $56.46   10.340%   $62.298   $62.30   $62.30   $62.30  
  Purchase #4 $76.73   9.306%   $83.8705   $83.87   $83.85   $83.90  
  Purchase #5 $80.77   6.776%   $86.243   $86.24   $86.25   $86.20  
  Purchase #6 $194.96   6.227%   $207.1002   $207.10   $207.10   $207.10  
  Purchase #7 $213.69   4.475%   $223.2526   $223.25   $223.25   $223.30  
  7 purchase totals = $873.31       $926.1613   $926.16   $926.15   $926.20