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	$99.60	12.146%	$111.6974	$111.70	$111.70	$111.70
Purchase #2	$204.98	3.533%	$212.2219	$212.22	$212.20	$212.20
Purchase #3	$127.75	7.247%	$137.008	$137.01	$137.00	$137.00
Purchase #4	$88.36	13.171%	$99.9979	$100.00	$100.00	$100.00
Purchase #5	$155.59	6.447%	$165.6209	$165.62	$165.60	$165.60
Purchase #6	$50.48	8.426%	$54.7334	$54.73	$54.75	$54.70
Purchase #7	$93.83	8.772%	$102.0608	$102.06	$102.05	$102.10
7 purchase totals =	$820.59		$883.3403	$883.34	$883.30	$883.30