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	$141.63	11.808%	$158.3537	$158.35	$158.35	$158.40
Purchase #2	$65.98	4.766%	$69.1246	$69.12	$69.10	$69.10
Purchase #3	$74.55	11.811%	$83.3551	$83.36	$83.35	$83.40
Purchase #4	$145.69	5.129%	$153.1624	$153.16	$153.15	$153.20
Purchase #5	$244.29	10.629%	$270.2556	$270.26	$270.25	$270.30
Purchase #6	$107.87	3.406%	$111.5441	$111.54	$111.55	$111.50
Purchase #7	$247.71	11.390%	$275.9242	$275.92	$275.90	$275.90
7 purchase totals =	$1,027.72		$1,121.7197	$1,121.71	$1,121.65	$1,121.80