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	$51.34	4.130%	$53.4603	$53.46	$53.45	$53.50
Purchase #2	$160.40	8.257%	$173.6442	$173.64	$173.65	$173.60
Purchase #3	$44.87	4.604%	$46.9358	$46.94	$46.95	$46.90
Purchase #4	$208.93	9.385%	$228.5381	$228.54	$228.55	$228.50
Purchase #5	$31.37	7.129%	$33.6064	$33.61	$33.60	$33.60
Purchase #6	$32.83	13.571%	$37.2854	$37.29	$37.30	$37.30
Purchase #7	$45.72	11.133%	$50.81	$50.81	$50.80	$50.80
7 purchase totals =	$575.46		$624.2802	$624.29	$624.30	$624.20