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	$55.89	4.191%	$58.2323	$58.23	$58.25	$58.20
Purchase #2	$24.77	7.864%	$26.7179	$26.72	$26.70	$26.70
Purchase #3	$117.57	8.144%	$127.1449	$127.14	$127.15	$127.10
Purchase #4	$150.82	13.764%	$171.5789	$171.58	$171.60	$171.60
Purchase #5	$209.86	5.575%	$221.5597	$221.56	$221.55	$221.60
Purchase #6	$164.27	5.691%	$173.6186	$173.62	$173.60	$173.60
Purchase #7	$12.38	8.291%	$13.4064	$13.41	$13.40	$13.40
7 purchase totals =	$735.56		$792.2587	$792.26	$792.25	$792.20