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	$211.58	5.749%	$223.7437	$223.74	$223.75	$223.70
Purchase #2	$43.31	11.149%	$48.1386	$48.14	$48.15	$48.10
Purchase #3	$66.31	7.844%	$71.5114	$71.51	$71.50	$71.50
Purchase #4	$229.65	3.636%	$238.0001	$238.00	$238.00	$238.00
Purchase #5	$34.65	8.368%	$37.5495	$37.55	$37.55	$37.50
Purchase #6	$168.39	4.741%	$176.3734	$176.37	$176.35	$176.40
Purchase #7	$86.37	4.195%	$89.9932	$89.99	$90.00	$90.00
7 purchase totals =	$840.26		$885.3099	$885.30	$885.30	$885.20