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	$145.75	8.643%	$158.3472	$158.35	$158.35	$158.30
Purchase #2	$154.54	11.413%	$172.1777	$172.18	$172.20	$172.20
Purchase #3	$223.94	9.574%	$245.38	$245.38	$245.40	$245.40
Purchase #4	$99.54	13.126%	$112.6056	$112.61	$112.60	$112.60
Purchase #5	$146.83	12.608%	$165.3423	$165.34	$165.35	$165.30
Purchase #6	$62.81	13.451%	$71.2586	$71.26	$71.25	$71.30
Purchase #7	$111.94	12.619%	$126.0657	$126.07	$126.05	$126.10
7 purchase totals =	$945.35		$1,051.1771	$1,051.19	$1,051.20	$1,051.20