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	$64.65	12.327%	$72.6194	$72.62	$72.60	$72.60
Purchase #2	$83.87	11.579%	$93.5813	$93.58	$93.60	$93.60
Purchase #3	$115.56	10.673%	$127.8937	$127.89	$127.90	$127.90
Purchase #4	$127.26	4.109%	$132.4891	$132.49	$132.50	$132.50
Purchase #5	$140.45	3.626%	$145.5427	$145.54	$145.55	$145.50
Purchase #6	$71.97	3.617%	$74.5732	$74.57	$74.55	$74.60
Purchase #7	$205.56	5.773%	$217.427	$217.43	$217.45	$217.40
7 purchase totals =	$809.32		$864.1264	$864.12	$864.15	$864.10