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 $204.50   9.874%   $224.6923   $224.69   $224.70   $224.70  
  Purchase #2 $48.30   10.373%   $53.3102   $53.31   $53.30   $53.30  
  Purchase #3 $243.47   7.706%   $262.2318   $262.23   $262.25   $262.20  
  Purchase #4 $29.82   10.554%   $32.9672   $32.97   $32.95   $33.00  
  Purchase #5 $167.52   5.264%   $176.3383   $176.34   $176.35   $176.30  
  Purchase #6 $65.85   7.728%   $70.9389   $70.94   $70.95   $70.90  
  Purchase #7 $222.70   7.567%   $239.5517   $239.55   $239.55   $239.60  
  7 purchase totals = $982.16       $1,060.0304   $1,060.03   $1,060.05   $1,060.00