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	$184.90	6.176%	$196.3194	$196.32	$196.30	$196.30
Purchase #2	$67.77	11.251%	$75.3948	$75.39	$75.40	$75.40
Purchase #3	$37.87	8.238%	$40.9897	$40.99	$41.00	$41.00
Purchase #4	$187.66	4.867%	$196.7934	$196.79	$196.80	$196.80
Purchase #5	$175.60	5.174%	$184.6855	$184.69	$184.70	$184.70
Purchase #6	$13.31	13.189%	$15.0655	$15.07	$15.05	$15.10
Purchase #7	$208.40	7.730%	$224.5093	$224.51	$224.50	$224.50
7 purchase totals =	$875.51		$933.7576	$933.76	$933.75	$933.80