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 $195.60   9.504%   $214.1898   $214.19   $214.20   $214.20  
  Purchase #2 $210.33   11.117%   $233.7124   $233.71   $233.70   $233.70  
  Purchase #3 $81.96   8.339%   $88.7946   $88.79   $88.80   $88.80  
  Purchase #4 $24.36   12.383%   $27.3765   $27.38   $27.40   $27.40  
  Purchase #5 $76.66   11.584%   $85.5403   $85.54   $85.55   $85.50  
  Purchase #6 $220.78   6.361%   $234.8238   $234.82   $234.80   $234.80  
  Purchase #7 $45.68   11.795%   $51.068   $51.07   $51.05   $51.10  
  7 purchase totals = $855.37       $935.5054   $935.50   $935.50   $935.50