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	$154.69	11.299%	$172.1684	$172.17	$172.15	$172.20
Purchase #2	$117.49	11.362%	$130.8392	$130.84	$130.85	$130.80
Purchase #3	$162.88	5.341%	$171.5794	$171.58	$171.60	$171.60
Purchase #4	$12.25	9.212%	$13.3785	$13.38	$13.40	$13.40
Purchase #5	$67.27	7.575%	$72.3657	$72.37	$72.35	$72.40
Purchase #6	$90.84	4.146%	$94.6062	$94.61	$94.60	$94.60
Purchase #7	$15.96	11.452%	$17.7877	$17.79	$17.80	$17.80
7 purchase totals =	$621.38		$672.7251	$672.74	$672.75	$672.80