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 $184.43   11.177%   $205.0437   $205.04   $205.05   $205.00  
  Purchase #2 $25.87   12.298%   $29.0515   $29.05   $29.05   $29.10  
  Purchase #3 $58.75   10.530%   $64.9364   $64.94   $64.95   $64.90  
  Purchase #4 $249.90   11.507%   $278.656   $278.66   $278.65   $278.70  
  Purchase #5 $200.71   7.651%   $216.0663   $216.07   $216.05   $216.10  
  Purchase #6 $190.70   4.607%   $199.4855   $199.49   $199.50   $199.50  
  Purchase #7 $141.73   10.163%   $156.134   $156.13   $156.15   $156.10  
  7 purchase totals = $1,052.09       $1,149.3734   $1,149.38   $1,149.40   $1,149.40