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	$41.66	12.633%	$46.9229	$46.92	$46.90	$46.90
Purchase #2	$188.46	13.754%	$214.3808	$214.38	$214.40	$214.40
Purchase #3	$242.35	13.566%	$275.2272	$275.23	$275.25	$275.20
Purchase #4	$116.58	9.202%	$127.3077	$127.31	$127.30	$127.30
Purchase #5	$105.85	10.409%	$116.8679	$116.87	$116.85	$116.90
Purchase #6	$157.57	4.218%	$164.2163	$164.22	$164.20	$164.20
Purchase #7	$249.48	11.265%	$277.5839	$277.58	$277.60	$277.60
7 purchase totals =	$1,101.95		$1,222.5067	$1,222.51	$1,222.50	$1,222.50