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	$58.93	11.848%	$65.912	$65.91	$65.90	$65.90
Purchase #2	$101.26	10.152%	$111.5399	$111.54	$111.55	$111.50
Purchase #3	$144.52	10.729%	$160.0256	$160.03	$160.05	$160.00
Purchase #4	$204.45	3.434%	$211.4708	$211.47	$211.45	$211.50
Purchase #5	$85.57	7.370%	$91.8765	$91.88	$91.90	$91.90
Purchase #6	$22.55	9.427%	$24.6758	$24.68	$24.70	$24.70
Purchase #7	$184.57	6.558%	$196.6741	$196.67	$196.65	$196.70
7 purchase totals =	$801.85		$862.1747	$862.18	$862.20	$862.20