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	$108.61	9.179%	$118.5793	$118.58	$118.60	$118.60
Purchase #2	$228.46	9.109%	$249.2704	$249.27	$249.25	$249.30
Purchase #3	$54.50	3.722%	$56.5285	$56.53	$56.55	$56.50
Purchase #4	$236.88	7.580%	$254.8355	$254.84	$254.85	$254.80
Purchase #5	$45.88	5.702%	$48.4961	$48.50	$48.50	$48.50
Purchase #6	$195.32	10.224%	$215.2895	$215.29	$215.30	$215.30
Purchase #7	$192.25	11.520%	$214.3972	$214.40	$214.40	$214.40
7 purchase totals =	$1,061.90		$1,157.3965	$1,157.41	$1,157.45	$1,157.40