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	$223.95	8.290%	$242.5155	$242.52	$242.50	$242.50
Purchase #2	$56.84	11.157%	$63.1816	$63.18	$63.20	$63.20
Purchase #3	$10.59	8.222%	$11.4607	$11.46	$11.45	$11.50
Purchase #4	$63.92	8.630%	$69.4363	$69.44	$69.45	$69.40
Purchase #5	$49.58	10.408%	$54.7403	$54.74	$54.75	$54.70
Purchase #6	$83.94	7.767%	$90.4596	$90.46	$90.45	$90.50
Purchase #7	$28.73	12.230%	$32.2437	$32.24	$32.25	$32.20
7 purchase totals =	$517.55		$564.0377	$564.04	$564.05	$564.00