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 $194.94   4.799%   $204.2952   $204.30   $204.30   $204.30  
  Purchase #2 $157.49   5.236%   $165.7362   $165.74   $165.75   $165.70  
  Purchase #3 $44.50   9.597%   $48.7707   $48.77   $48.75   $48.80  
  Purchase #4 $45.90   10.849%   $50.8797   $50.88   $50.90   $50.90  
  Purchase #5 $89.88   9.707%   $98.6047   $98.60   $98.60   $98.60  
  Purchase #6 $166.72   12.786%   $188.0368   $188.04   $188.05   $188.00  
  Purchase #7 $180.64   6.556%   $192.4828   $192.48   $192.50   $192.50  
  7 purchase totals = $880.07       $948.8061   $948.81   $948.85   $948.80