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	$64.61	4.493%	$67.5129	$67.51	$67.50	$67.50
Purchase #2	$118.62	12.433%	$133.368	$133.37	$133.35	$133.40
Purchase #3	$13.86	7.667%	$14.9226	$14.92	$14.90	$14.90
Purchase #4	$172.79	6.393%	$183.8365	$183.84	$183.85	$183.80
Purchase #5	$100.26	10.621%	$110.9086	$110.91	$110.90	$110.90
Purchase #6	$42.69	8.845%	$46.4659	$46.47	$46.45	$46.50
Purchase #7	$132.56	11.111%	$147.2887	$147.29	$147.30	$147.30
7 purchase totals =	$645.39		$704.3032	$704.31	$704.25	$704.30