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	$213.60	3.520%	$221.1187	$221.12	$221.10	$221.10
Purchase #2	$82.29	9.817%	$90.3684	$90.37	$90.35	$90.40
Purchase #3	$214.43	12.772%	$241.817	$241.82	$241.80	$241.80
Purchase #4	$204.85	10.112%	$225.5644	$225.56	$225.55	$225.60
Purchase #5	$56.42	10.578%	$62.3881	$62.39	$62.40	$62.40
Purchase #6	$100.33	6.495%	$106.8464	$106.85	$106.85	$106.80
Purchase #7	$64.56	10.783%	$71.5215	$71.52	$71.50	$71.50
7 purchase totals =	$936.48		$1,019.6245	$1,019.63	$1,019.55	$1,019.60