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	$192.85	11.117%	$214.2891	$214.29	$214.30	$214.30
Purchase #2	$26.51	4.470%	$27.695	$27.70	$27.70	$27.70
Purchase #3	$97.65	13.627%	$110.9568	$110.96	$110.95	$111.00
Purchase #4	$83.88	6.653%	$89.4605	$89.46	$89.45	$89.50
Purchase #5	$11.50	3.342%	$11.8843	$11.88	$11.90	$11.90
Purchase #6	$125.35	9.637%	$137.43	$137.43	$137.45	$137.40
Purchase #7	$81.72	7.749%	$88.0525	$88.05	$88.05	$88.10
7 purchase totals =	$619.46		$679.7682	$679.77	$679.80	$679.90