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	$112.27	3.759%	$116.4902	$116.49	$116.50	$116.50
Purchase #2	$10.94	5.497%	$11.5414	$11.54	$11.55	$11.50
Purchase #3	$88.77	12.301%	$99.6896	$99.69	$99.70	$99.70
Purchase #4	$241.87	7.854%	$260.8665	$260.87	$260.85	$260.90
Purchase #5	$25.54	11.765%	$28.5448	$28.54	$28.55	$28.50
Purchase #6	$234.48	8.848%	$255.2268	$255.23	$255.25	$255.20
Purchase #7	$21.29	6.413%	$22.6553	$22.66	$22.65	$22.70
7 purchase totals =	$735.16		$795.0146	$795.02	$795.05	$795.00