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	$47.64	4.485%	$49.7767	$49.78	$49.80	$49.80
Purchase #2	$32.72	4.166%	$34.0831	$34.08	$34.10	$34.10
Purchase #3	$214.27	7.728%	$230.8288	$230.83	$230.85	$230.80
Purchase #4	$176.67	13.217%	$200.0205	$200.02	$200.00	$200.00
Purchase #5	$241.29	6.437%	$256.8218	$256.82	$256.80	$256.80
Purchase #6	$66.41	8.172%	$71.837	$71.84	$71.85	$71.80
Purchase #7	$197.77	3.155%	$204.0096	$204.01	$204.00	$204.00
7 purchase totals =	$976.77		$1,047.3775	$1,047.38	$1,047.40	$1,047.30