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	$224.94	8.498%	$244.0554	$244.06	$244.05	$244.10
Purchase #2	$28.82	12.781%	$32.5035	$32.50	$32.50	$32.50
Purchase #3	$226.93	8.224%	$245.5927	$245.59	$245.60	$245.60
Purchase #4	$205.67	9.793%	$225.8113	$225.81	$225.80	$225.80
Purchase #5	$162.43	6.364%	$172.767	$172.77	$172.75	$172.80
Purchase #6	$35.56	4.841%	$37.2815	$37.28	$37.30	$37.30
Purchase #7	$11.37	5.114%	$11.9515	$11.95	$11.95	$12.00
7 purchase totals =	$895.72		$969.9629	$969.96	$969.95	$970.10