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	$74.39	5.242%	$78.2895	$78.29	$78.30	$78.30
Purchase #2	$203.82	4.341%	$212.6678	$212.67	$212.65	$212.70
Purchase #3	$132.41	3.348%	$136.8431	$136.84	$136.85	$136.80
Purchase #4	$98.51	13.403%	$111.7133	$111.71	$111.70	$111.70
Purchase #5	$232.55	7.822%	$250.7401	$250.74	$250.75	$250.70
Purchase #6	$66.52	13.428%	$75.4523	$75.45	$75.45	$75.50
Purchase #7	$190.30	13.842%	$216.6413	$216.64	$216.65	$216.60
7 purchase totals =	$998.50		$1,082.3474	$1,082.34	$1,082.35	$1,082.30