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	$248.37	5.682%	$262.4824	$262.48	$262.50	$262.50
Purchase #2	$127.89	10.495%	$141.3121	$141.31	$141.30	$141.30
Purchase #3	$52.68	12.224%	$59.1196	$59.12	$59.10	$59.10
Purchase #4	$9.58	5.757%	$10.1315	$10.13	$10.15	$10.10
Purchase #5	$153.70	8.282%	$166.4294	$166.43	$166.45	$166.40
Purchase #6	$178.56	3.415%	$184.6578	$184.66	$184.65	$184.70
Purchase #7	$46.52	4.638%	$48.6776	$48.68	$48.70	$48.70
7 purchase totals =	$817.30		$872.8104	$872.81	$872.85	$872.80