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	$40.35	11.606%	$45.033	$45.03	$45.05	$45.00
Purchase #2	$116.81	6.260%	$124.1223	$124.12	$124.10	$124.10
Purchase #3	$59.51	3.408%	$61.5381	$61.54	$61.55	$61.50
Purchase #4	$138.83	10.722%	$153.7154	$153.72	$153.70	$153.70
Purchase #5	$23.52	3.785%	$24.4102	$24.41	$24.40	$24.40
Purchase #6	$78.97	5.611%	$83.401	$83.40	$83.40	$83.40
Purchase #7	$71.76	9.318%	$78.4466	$78.45	$78.45	$78.40
7 purchase totals =	$529.75		$570.6666	$570.67	$570.65	$570.50