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	$43.50	6.332%	$46.2544	$46.25	$46.25	$46.30
Purchase #2	$116.33	11.849%	$130.1139	$130.11	$130.10	$130.10
Purchase #3	$193.60	7.663%	$208.4356	$208.44	$208.45	$208.40
Purchase #4	$38.87	4.394%	$40.5779	$40.58	$40.60	$40.60
Purchase #5	$102.52	8.838%	$111.5807	$111.58	$111.60	$111.60
Purchase #6	$159.43	6.825%	$170.3111	$170.31	$170.30	$170.30
Purchase #7	$13.44	8.641%	$14.6014	$14.60	$14.60	$14.60
7 purchase totals =	$667.69		$721.8750	$721.87	$721.90	$721.90