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	$78.47	4.721%	$82.1746	$82.17	$82.15	$82.20
Purchase #2	$214.67	7.723%	$231.249	$231.25	$231.25	$231.20
Purchase #3	$35.28	6.592%	$37.6057	$37.61	$37.60	$37.60
Purchase #4	$118.63	6.261%	$126.0574	$126.06	$126.05	$126.10
Purchase #5	$196.62	6.500%	$209.4003	$209.40	$209.40	$209.40
Purchase #6	$89.70	13.429%	$101.7458	$101.75	$101.75	$101.70
Purchase #7	$166.94	3.781%	$173.252	$173.25	$173.25	$173.30
7 purchase totals =	$900.31		$961.4848	$961.49	$961.45	$961.50