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	$131.34	11.784%	$146.8171	$146.82	$146.80	$146.80
Purchase #2	$13.48	8.698%	$14.6525	$14.65	$14.65	$14.70
Purchase #3	$248.86	5.553%	$262.6792	$262.68	$262.70	$262.70
Purchase #4	$13.27	7.139%	$14.2173	$14.22	$14.20	$14.20
Purchase #5	$220.34	4.231%	$229.6626	$229.66	$229.65	$229.70
Purchase #6	$76.72	7.384%	$82.385	$82.39	$82.40	$82.40
Purchase #7	$215.51	10.847%	$238.8864	$238.89	$238.90	$238.90
7 purchase totals =	$919.52		$989.3001	$989.31	$989.30	$989.40