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	$245.48	4.657%	$256.912	$256.91	$256.90	$256.90
Purchase #2	$151.42	13.800%	$172.316	$172.32	$172.30	$172.30
Purchase #3	$212.27	8.158%	$229.587	$229.59	$229.60	$229.60
Purchase #4	$119.28	6.643%	$127.2038	$127.20	$127.20	$127.20
Purchase #5	$203.33	13.386%	$230.5478	$230.55	$230.55	$230.50
Purchase #6	$199.75	8.776%	$217.2801	$217.28	$217.30	$217.30
Purchase #7	$29.66	9.437%	$32.459	$32.46	$32.45	$32.50
7 purchase totals =	$1,161.19		$1,266.3057	$1,266.31	$1,266.30	$1,266.30