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 $182.26   7.281%   $195.5304   $195.53   $195.55   $195.50  
  Purchase #2 $138.38   3.313%   $142.9645   $142.96   $142.95   $143.00  
  Purchase #3 $158.55   8.256%   $171.6399   $171.64   $171.65   $171.60  
  Purchase #4 $87.49   3.298%   $90.3754   $90.38   $90.40   $90.40  
  Purchase #5 $138.55   5.798%   $146.5831   $146.58   $146.60   $146.60  
  Purchase #6 $54.54   3.215%   $56.2935   $56.29   $56.30   $56.30  
  Purchase #7 $72.49   9.519%   $79.3903   $79.39   $79.40   $79.40  
  7 purchase totals = $832.26       $882.7771   $882.77   $882.85   $882.80