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 $214.28   12.485%   $241.0329   $241.03   $241.05   $241.00  
  Purchase #2 $62.33   8.696%   $67.7502   $67.75   $67.75   $67.80  
  Purchase #3 $16.61   13.535%   $18.8582   $18.86   $18.85   $18.90  
  Purchase #4 $84.26   10.707%   $93.2817   $93.28   $93.30   $93.30  
  Purchase #5 $60.97   7.682%   $65.6537   $65.65   $65.65   $65.70  
  Purchase #6 $47.60   7.289%   $51.0696   $51.07   $51.05   $51.10  
  Purchase #7 $186.73   4.609%   $195.3364   $195.34   $195.35   $195.30  
  7 purchase totals = $672.78       $732.9827   $732.98   $733.00   $733.10