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 $84.39   13.634%   $95.8957   $95.90   $95.90   $95.90  
  Purchase #2 $68.28   9.487%   $74.7577   $74.76   $74.75   $74.80  
  Purchase #3 $51.93   12.257%   $58.2951   $58.30   $58.30   $58.30  
  Purchase #4 $188.68   3.790%   $195.831   $195.83   $195.85   $195.80  
  Purchase #5 $184.59   8.456%   $200.1989   $200.20   $200.20   $200.20  
  Purchase #6 $59.89   4.488%   $62.5779   $62.58   $62.60   $62.60  
  Purchase #7 $34.36   4.643%   $35.9553   $35.96   $35.95   $36.00  
  7 purchase totals = $672.12       $723.5116   $723.53   $723.55   $723.60