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	$110.60	5.279%	$116.4386	$116.44	$116.45	$116.40
Purchase #2	$243.70	13.209%	$275.8903	$275.89	$275.90	$275.90
Purchase #3	$40.35	3.252%	$41.6622	$41.66	$41.65	$41.70
Purchase #4	$188.97	3.789%	$196.1301	$196.13	$196.15	$196.10
Purchase #5	$57.66	3.644%	$59.7611	$59.76	$59.75	$59.80
Purchase #6	$10.73	7.250%	$11.5079	$11.51	$11.50	$11.50
Purchase #7	$194.57	13.810%	$221.4401	$221.44	$221.45	$221.40
7 purchase totals =	$846.58		$922.8303	$922.83	$922.85	$922.80