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	$153.65	5.535%	$162.1545	$162.15	$162.15	$162.20
Purchase #2	$83.42	7.714%	$89.855	$89.86	$89.85	$89.90
Purchase #3	$7.62	10.483%	$8.4188	$8.42	$8.40	$8.40
Purchase #4	$43.43	11.309%	$48.3415	$48.34	$48.35	$48.30
Purchase #5	$155.54	4.547%	$162.6124	$162.61	$162.60	$162.60
Purchase #6	$8.27	5.620%	$8.7348	$8.73	$8.75	$8.70
Purchase #7	$10.49	4.485%	$10.9605	$10.96	$10.95	$11.00
7 purchase totals =	$462.42		$491.0775	$491.07	$491.05	$491.10