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	$110.56	3.482%	$114.4097	$114.41	$114.40	$114.40
Purchase #2	$97.32	6.260%	$103.4122	$103.41	$103.40	$103.40
Purchase #3	$88.34	13.249%	$100.0442	$100.04	$100.05	$100.00
Purchase #4	$111.72	5.332%	$117.6769	$117.68	$117.70	$117.70
Purchase #5	$33.75	9.674%	$37.015	$37.02	$37.00	$37.00
Purchase #6	$188.55	4.635%	$197.2893	$197.29	$197.30	$197.30
Purchase #7	$211.52	4.757%	$221.582	$221.58	$221.60	$221.60
7 purchase totals =	$841.76		$891.4293	$891.43	$891.45	$891.40