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 $92.66   3.505%   $95.9077   $95.91   $95.90   $95.90  
  Purchase #2 $93.80   3.568%   $97.1468   $97.15   $97.15   $97.10  
  Purchase #3 $15.75   13.377%   $17.8569   $17.86   $17.85   $17.90  
  Purchase #4 $243.88   4.114%   $253.9132   $253.91   $253.90   $253.90  
  Purchase #5 $225.61   11.438%   $251.4153   $251.42   $251.40   $251.40  
  Purchase #6 $203.69   11.865%   $227.8578   $227.86   $227.85   $227.90  
  Purchase #7 $194.60   13.708%   $221.2758   $221.28   $221.30   $221.30  
  7 purchase totals = $1,069.99       $1,165.3735   $1,165.39   $1,165.35   $1,165.40