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	$37.71	3.792%	$39.14	$39.14	$39.15	$39.10
Purchase #2	$71.81	13.782%	$81.7069	$81.71	$81.70	$81.70
Purchase #3	$217.55	12.692%	$245.1614	$245.16	$245.15	$245.20
Purchase #4	$81.71	9.794%	$89.7127	$89.71	$89.70	$89.70
Purchase #5	$153.63	7.566%	$165.2536	$165.25	$165.25	$165.30
Purchase #6	$147.37	7.396%	$158.2695	$158.27	$158.25	$158.30
Purchase #7	$244.66	4.752%	$256.2862	$256.29	$256.30	$256.30
7 purchase totals =	$954.44		$1,035.5303	$1,035.53	$1,035.50	$1,035.60