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	$58.85	12.773%	$66.3669	$66.37	$66.35	$66.40
Purchase #2	$196.27	9.413%	$214.7449	$214.74	$214.75	$214.70
Purchase #3	$234.64	12.739%	$264.5308	$264.53	$264.55	$264.50
Purchase #4	$205.32	3.697%	$212.9107	$212.91	$212.90	$212.90
Purchase #5	$171.37	3.153%	$176.7733	$176.77	$176.75	$176.80
Purchase #6	$92.72	7.184%	$99.381	$99.38	$99.40	$99.40
Purchase #7	$173.52	9.191%	$189.4682	$189.47	$189.45	$189.50
7 purchase totals =	$1,132.69		$1,224.1758	$1,224.17	$1,224.15	$1,224.20