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	$64.29	5.290%	$67.6909	$67.69	$67.70	$67.70
Purchase #2	$112.27	10.682%	$124.2627	$124.26	$124.25	$124.30
Purchase #3	$81.71	4.724%	$85.57	$85.57	$85.55	$85.60
Purchase #4	$167.39	12.598%	$188.4778	$188.48	$188.50	$188.50
Purchase #5	$12.83	9.176%	$14.0073	$14.01	$14.00	$14.00
Purchase #6	$136.59	3.151%	$140.894	$140.89	$140.90	$140.90
Purchase #7	$209.58	5.741%	$221.612	$221.61	$221.60	$221.60
7 purchase totals =	$784.66		$842.5147	$842.51	$842.50	$842.60