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 $121.47   3.207%   $125.3655   $125.37   $125.35   $125.40  
  Purchase #2 $85.98   11.756%   $96.0878   $96.09   $96.10   $96.10  
  Purchase #3 $54.53   7.697%   $58.7272   $58.73   $58.75   $58.70  
  Purchase #4 $233.28   13.631%   $265.0784   $265.08   $265.10   $265.10  
  Purchase #5 $201.93   9.749%   $221.6162   $221.62   $221.60   $221.60  
  Purchase #6 $233.33   11.689%   $260.6039   $260.60   $260.60   $260.60  
  Purchase #7 $168.26   11.386%   $187.4181   $187.42   $187.40   $187.40  
  7 purchase totals = $1,098.78       $1,214.8971   $1,214.91   $1,214.90   $1,214.90