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	$164.50	6.628%	$175.4031	$175.40	$175.40	$175.40
Purchase #2	$88.44	13.267%	$100.1733	$100.17	$100.15	$100.20
Purchase #3	$172.59	13.864%	$196.5179	$196.52	$196.50	$196.50
Purchase #4	$184.86	8.596%	$200.7506	$200.75	$200.75	$200.80
Purchase #5	$224.60	9.740%	$246.476	$246.48	$246.50	$246.50
Purchase #6	$104.81	5.213%	$110.2737	$110.27	$110.25	$110.30
Purchase #7	$221.42	11.759%	$247.4568	$247.46	$247.45	$247.50
7 purchase totals =	$1,161.22		$1,277.0514	$1,277.05	$1,277.00	$1,277.20