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	$248.97	7.476%	$267.583	$267.58	$267.60	$267.60
Purchase #2	$9.32	13.651%	$10.5923	$10.59	$10.60	$10.60
Purchase #3	$71.54	5.177%	$75.2436	$75.24	$75.25	$75.20
Purchase #4	$143.66	6.872%	$153.5323	$153.53	$153.55	$153.50
Purchase #5	$117.59	5.177%	$123.6776	$123.68	$123.70	$123.70
Purchase #6	$99.87	11.714%	$111.5688	$111.57	$111.55	$111.60
Purchase #7	$116.44	11.871%	$130.2626	$130.26	$130.25	$130.30
7 purchase totals =	$807.39		$872.4602	$872.45	$872.50	$872.50