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	$105.61	3.805%	$109.6285	$109.63	$109.65	$109.60
Purchase #2	$226.82	4.825%	$237.7641	$237.76	$237.75	$237.80
Purchase #3	$200.67	10.566%	$221.8728	$221.87	$221.85	$221.90
Purchase #4	$133.37	12.723%	$150.3387	$150.34	$150.35	$150.30
Purchase #5	$146.91	12.496%	$165.2679	$165.27	$165.25	$165.30
Purchase #6	$235.61	7.547%	$253.3915	$253.39	$253.40	$253.40
Purchase #7	$19.72	7.210%	$21.1418	$21.14	$21.15	$21.10
7 purchase totals =	$1,068.71		$1,159.4053	$1,159.40	$1,159.40	$1,159.40