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 $244.57   9.810%   $268.5623   $268.56   $268.55   $268.60  
  Purchase #2 $179.75   8.121%   $194.3475   $194.35   $194.35   $194.30  
  Purchase #3 $26.71   12.513%   $30.0522   $30.05   $30.05   $30.10  
  Purchase #4 $157.35   5.338%   $165.7493   $165.75   $165.75   $165.70  
  Purchase #5 $140.75   5.205%   $148.076   $148.08   $148.10   $148.10  
  Purchase #6 $210.86   6.216%   $223.9671   $223.97   $223.95   $224.00  
  Purchase #7 $163.64   13.507%   $185.7429   $185.74   $185.75   $185.70  
  7 purchase totals = $1,123.63       $1,216.4973   $1,216.50   $1,216.50   $1,216.50