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	$33.45	11.623%	$37.3379	$37.34	$37.35	$37.30
Purchase #2	$12.28	5.109%	$12.9074	$12.91	$12.90	$12.90
Purchase #3	$241.32	5.479%	$254.5419	$254.54	$254.55	$254.50
Purchase #4	$105.48	12.348%	$118.5047	$118.50	$118.50	$118.50
Purchase #5	$230.28	9.192%	$251.4473	$251.45	$251.45	$251.40
Purchase #6	$191.25	10.200%	$210.7575	$210.76	$210.75	$210.80
Purchase #7	$48.49	4.261%	$50.5562	$50.56	$50.55	$50.60
7 purchase totals =	$862.55		$936.0529	$936.06	$936.05	$936.00