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	$66.66	11.198%	$74.1246	$74.12	$74.10	$74.10
Purchase #2	$92.75	8.131%	$100.2915	$100.29	$100.30	$100.30
Purchase #3	$99.29	13.337%	$112.5323	$112.53	$112.55	$112.50
Purchase #4	$19.75	4.411%	$20.6212	$20.62	$20.60	$20.60
Purchase #5	$68.50	6.761%	$73.1313	$73.13	$73.15	$73.10
Purchase #6	$40.31	13.584%	$45.7857	$45.79	$45.80	$45.80
Purchase #7	$78.99	12.359%	$88.7524	$88.75	$88.75	$88.80
7 purchase totals =	$466.25		$515.2390	$515.23	$515.25	$515.20