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	$105.66	5.104%	$111.0529	$111.05	$111.05	$111.10
Purchase #2	$183.56	9.175%	$200.4016	$200.40	$200.40	$200.40
Purchase #3	$116.58	9.364%	$127.4966	$127.50	$127.50	$127.50
Purchase #4	$226.58	11.375%	$252.3535	$252.35	$252.35	$252.40
Purchase #5	$29.70	13.480%	$33.7036	$33.70	$33.70	$33.70
Purchase #6	$61.60	5.871%	$65.2165	$65.22	$65.20	$65.20
Purchase #7	$60.65	9.227%	$66.2462	$66.25	$66.25	$66.20
7 purchase totals =	$784.33		$856.4709	$856.47	$856.45	$856.50