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	$111.99	13.474%	$127.0795	$127.08	$127.10	$127.10
Purchase #2	$48.31	7.657%	$52.0091	$52.01	$52.00	$52.00
Purchase #3	$247.32	12.184%	$277.4535	$277.45	$277.45	$277.50
Purchase #4	$40.43	7.173%	$43.33	$43.33	$43.35	$43.30
Purchase #5	$154.63	10.146%	$170.3188	$170.32	$170.30	$170.30
Purchase #6	$67.45	11.297%	$75.0698	$75.07	$75.05	$75.10
Purchase #7	$136.46	7.242%	$146.3424	$146.34	$146.35	$146.30
7 purchase totals =	$806.59		$891.6031	$891.60	$891.60	$891.60