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	$182.34	5.547%	$192.4544	$192.45	$192.45	$192.50
Purchase #2	$145.49	13.689%	$165.4061	$165.41	$165.40	$165.40
Purchase #3	$212.79	10.680%	$235.516	$235.52	$235.50	$235.50
Purchase #4	$80.58	13.533%	$91.4849	$91.48	$91.50	$91.50
Purchase #5	$109.75	11.258%	$122.1057	$122.11	$122.10	$122.10
Purchase #6	$173.36	9.839%	$190.4169	$190.42	$190.40	$190.40
Purchase #7	$44.62	4.213%	$46.4998	$46.50	$46.50	$46.50
7 purchase totals =	$948.93		$1,043.8838	$1,043.89	$1,043.85	$1,043.90