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	$140.36	3.388%	$145.1154	$145.12	$145.10	$145.10
Purchase #2	$93.56	8.859%	$101.8485	$101.85	$101.85	$101.80
Purchase #3	$46.26	6.252%	$49.1522	$49.15	$49.15	$49.20
Purchase #4	$173.31	13.431%	$196.5873	$196.59	$196.60	$196.60
Purchase #5	$64.84	11.639%	$72.3867	$72.39	$72.40	$72.40
Purchase #6	$99.26	12.569%	$111.736	$111.74	$111.75	$111.70
Purchase #7	$154.49	3.339%	$159.6484	$159.65	$159.65	$159.60
7 purchase totals =	$772.08		$836.4745	$836.49	$836.50	$836.40