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 $144.75   5.667%   $152.953   $152.95   $152.95   $153.00  
  Purchase #2 $5.72   13.693%   $6.5032   $6.50   $6.50   $6.50  
  Purchase #3 $108.75   5.547%   $114.7824   $114.78   $114.80   $114.80  
  Purchase #4 $125.96   3.514%   $130.3862   $130.39   $130.40   $130.40  
  Purchase #5 $146.48   7.516%   $157.4894   $157.49   $157.50   $157.50  
  Purchase #6 $110.39   3.178%   $113.8982   $113.90   $113.90   $113.90  
  Purchase #7 $186.96   4.627%   $195.6106   $195.61   $195.60   $195.60  
  7 purchase totals = $829.01       $871.6230   $871.62   $871.65   $871.70