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 $160.28   5.534%   $169.1499   $169.15   $169.15   $169.10  
  Purchase #2 $180.41   8.252%   $195.2974   $195.30   $195.30   $195.30  
  Purchase #3 $76.43   4.603%   $79.9481   $79.95   $79.95   $79.90  
  Purchase #4 $168.95   4.170%   $175.9952   $176.00   $176.00   $176.00  
  Purchase #5 $241.68   13.216%   $273.6204   $273.62   $273.60   $273.60  
  Purchase #6 $236.76   8.338%   $256.501   $256.50   $256.50   $256.50  
  Purchase #7 $60.78   3.846%   $63.1176   $63.12   $63.10   $63.10  
  7 purchase totals = $1,125.29       $1,213.6296   $1,213.64   $1,213.60   $1,213.50