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	$185.66	4.577%	$194.1577	$194.16	$194.15	$194.20
Purchase #2	$118.26	7.758%	$127.4346	$127.43	$127.45	$127.40
Purchase #3	$95.39	8.239%	$103.2492	$103.25	$103.25	$103.20
Purchase #4	$221.73	9.758%	$243.3664	$243.37	$243.35	$243.40
Purchase #5	$248.62	10.245%	$274.0911	$274.09	$274.10	$274.10
Purchase #6	$104.36	6.797%	$111.4533	$111.45	$111.45	$111.50
Purchase #7	$215.26	13.573%	$244.4772	$244.48	$244.50	$244.50
7 purchase totals =	$1,189.28		$1,298.2295	$1,298.23	$1,298.25	$1,298.30