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	$138.86	10.110%	$152.8987	$152.90	$152.90	$152.90
Purchase #2	$59.40	9.863%	$65.2586	$65.26	$65.25	$65.30
Purchase #3	$61.97	7.259%	$66.4684	$66.47	$66.45	$66.50
Purchase #4	$94.56	11.261%	$105.2084	$105.21	$105.20	$105.20
Purchase #5	$20.29	10.326%	$22.3851	$22.39	$22.40	$22.40
Purchase #6	$228.31	6.390%	$242.899	$242.90	$242.90	$242.90
Purchase #7	$222.84	3.734%	$231.1608	$231.16	$231.15	$231.20
7 purchase totals =	$826.23		$886.2790	$886.29	$886.25	$886.40