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	$57.50	4.361%	$60.0076	$60.01	$60.00	$60.00
Purchase #2	$117.87	7.511%	$126.7232	$126.72	$126.70	$126.70
Purchase #3	$178.62	9.856%	$196.2248	$196.22	$196.20	$196.20
Purchase #4	$208.60	3.809%	$216.5456	$216.55	$216.55	$216.50
Purchase #5	$150.73	9.784%	$165.4774	$165.48	$165.50	$165.50
Purchase #6	$26.53	10.392%	$29.287	$29.29	$29.30	$29.30
Purchase #7	$190.45	11.712%	$212.7555	$212.76	$212.75	$212.80
7 purchase totals =	$930.30		$1,007.0211	$1,007.03	$1,007.00	$1,007.00