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	$108.71	3.785%	$112.8247	$112.82	$112.80	$112.80
Purchase #2	$22.66	8.552%	$24.5979	$24.60	$24.60	$24.60
Purchase #3	$243.96	13.675%	$277.3215	$277.32	$277.30	$277.30
Purchase #4	$13.90	6.345%	$14.782	$14.78	$14.80	$14.80
Purchase #5	$136.61	13.673%	$155.2887	$155.29	$155.30	$155.30
Purchase #6	$42.41	6.778%	$45.2845	$45.28	$45.30	$45.30
Purchase #7	$114.82	10.786%	$127.2045	$127.20	$127.20	$127.20
7 purchase totals =	$683.07		$757.3038	$757.29	$757.30	$757.30