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	$185.92	8.247%	$201.2528	$201.25	$201.25	$201.30
Purchase #2	$89.78	10.794%	$99.4709	$99.47	$99.45	$99.50
Purchase #3	$249.48	11.359%	$277.8184	$277.82	$277.80	$277.80
Purchase #4	$76.52	7.694%	$82.4074	$82.41	$82.40	$82.40
Purchase #5	$10.79	5.111%	$11.3415	$11.34	$11.35	$11.30
Purchase #6	$48.93	12.481%	$55.037	$55.04	$55.05	$55.00
Purchase #7	$146.29	8.532%	$158.7715	$158.77	$158.75	$158.80
7 purchase totals =	$807.71		$886.0995	$886.10	$886.05	$886.10