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	$239.62	6.555%	$255.3271	$255.33	$255.35	$255.30
Purchase #2	$158.35	10.433%	$174.8707	$174.87	$174.85	$174.90
Purchase #3	$18.34	10.667%	$20.2963	$20.30	$20.30	$20.30
Purchase #4	$153.89	7.714%	$165.7611	$165.76	$165.75	$165.80
Purchase #5	$174.77	7.322%	$187.5667	$187.57	$187.55	$187.60
Purchase #6	$110.77	3.420%	$114.5583	$114.56	$114.55	$114.60
Purchase #7	$40.27	9.673%	$44.1653	$44.17	$44.15	$44.20
7 purchase totals =	$896.01		$962.5455	$962.56	$962.50	$962.70