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 $85.36   12.766%   $96.2571   $96.26   $96.25   $96.30  
  Purchase #2 $141.89   8.745%   $154.2983   $154.30   $154.30   $154.30  
  Purchase #3 $169.35   11.838%   $189.3977   $189.40   $189.40   $189.40  
  Purchase #4 $244.86   9.689%   $268.5845   $268.58   $268.60   $268.60  
  Purchase #5 $66.76   4.663%   $69.873   $69.87   $69.85   $69.90  
  Purchase #6 $142.58   7.526%   $153.3106   $153.31   $153.30   $153.30  
  Purchase #7 $104.72   11.451%   $116.7115   $116.71   $116.70   $116.70  
  7 purchase totals = $955.52       $1,048.4327   $1,048.43   $1,048.40   $1,048.50