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	$55.27	11.450%	$61.5984	$61.60	$61.60	$61.60
Purchase #2	$211.62	10.212%	$233.2306	$233.23	$233.25	$233.20
Purchase #3	$63.55	12.386%	$71.4213	$71.42	$71.40	$71.40
Purchase #4	$35.33	4.504%	$36.9213	$36.92	$36.90	$36.90
Purchase #5	$111.68	13.192%	$126.4128	$126.41	$126.40	$126.40
Purchase #6	$120.35	8.733%	$130.8602	$130.86	$130.85	$130.90
Purchase #7	$235.65	8.628%	$255.9819	$255.98	$256.00	$256.00
7 purchase totals =	$833.45		$916.4265	$916.42	$916.40	$916.40