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	$148.48	6.595%	$158.2723	$158.27	$158.25	$158.30
Purchase #2	$231.69	9.761%	$254.3053	$254.31	$254.30	$254.30
Purchase #3	$194.43	10.250%	$214.3591	$214.36	$214.35	$214.40
Purchase #4	$13.64	8.325%	$14.7755	$14.78	$14.80	$14.80
Purchase #5	$54.50	11.564%	$60.8024	$60.80	$60.80	$60.80
Purchase #6	$160.53	3.327%	$165.8708	$165.87	$165.85	$165.90
Purchase #7	$72.77	7.569%	$78.278	$78.28	$78.30	$78.30
7 purchase totals =	$876.04		$946.6634	$946.67	$946.65	$946.80