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	$45.94	13.460%	$52.1235	$52.12	$52.10	$52.10
Purchase #2	$131.91	7.680%	$142.0407	$142.04	$142.05	$142.00
Purchase #3	$73.58	6.189%	$78.1339	$78.13	$78.15	$78.10
Purchase #4	$137.73	5.719%	$145.6068	$145.61	$145.60	$145.60
Purchase #5	$167.44	9.397%	$183.1743	$183.17	$183.15	$183.20
Purchase #6	$140.52	8.626%	$152.6413	$152.64	$152.65	$152.60
Purchase #7	$174.95	13.418%	$198.4248	$198.42	$198.40	$198.40
7 purchase totals =	$872.07		$952.1453	$952.13	$952.10	$952.00