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	$213.25	9.552%	$233.6196	$233.62	$233.60	$233.60
Purchase #2	$132.39	10.663%	$146.5067	$146.51	$146.50	$146.50
Purchase #3	$243.96	11.313%	$271.5592	$271.56	$271.55	$271.60
Purchase #4	$111.98	5.774%	$118.4457	$118.45	$118.45	$118.40
Purchase #5	$29.71	8.412%	$32.2092	$32.21	$32.20	$32.20
Purchase #6	$131.27	6.276%	$139.5085	$139.51	$139.50	$139.50
Purchase #7	$178.41	4.167%	$185.8443	$185.84	$185.85	$185.80
7 purchase totals =	$1,040.97		$1,127.6932	$1,127.70	$1,127.65	$1,127.60