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	$146.45	7.863%	$157.9654	$157.97	$157.95	$158.00
Purchase #2	$78.52	12.406%	$88.2612	$88.26	$88.25	$88.30
Purchase #3	$37.41	8.273%	$40.5049	$40.50	$40.50	$40.50
Purchase #4	$40.79	6.506%	$43.4438	$43.44	$43.45	$43.40
Purchase #5	$17.56	5.327%	$18.4954	$18.50	$18.50	$18.50
Purchase #6	$40.65	4.685%	$42.5545	$42.55	$42.55	$42.60
Purchase #7	$110.79	4.763%	$116.0669	$116.07	$116.05	$116.10
7 purchase totals =	$472.17		$507.2921	$507.29	$507.25	$507.40