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	$41.28	12.471%	$46.428	$46.43	$46.45	$46.40
Purchase #2	$200.62	9.598%	$219.8755	$219.88	$219.90	$219.90
Purchase #3	$127.78	13.544%	$145.0865	$145.09	$145.10	$145.10
Purchase #4	$247.43	11.485%	$275.8473	$275.85	$275.85	$275.80
Purchase #5	$167.49	7.824%	$180.5944	$180.59	$180.60	$180.60
Purchase #6	$159.98	10.404%	$176.6243	$176.62	$176.60	$176.60
Purchase #7	$143.48	8.684%	$155.9398	$155.94	$155.95	$155.90
7 purchase totals =	$1,088.06		$1,200.3958	$1,200.40	$1,200.45	$1,200.30