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	$211.83	8.393%	$229.6089	$229.61	$229.60	$229.60
Purchase #2	$155.30	3.679%	$161.0135	$161.01	$161.00	$161.00
Purchase #3	$34.95	4.672%	$36.5829	$36.58	$36.60	$36.60
Purchase #4	$112.31	10.290%	$123.8667	$123.87	$123.85	$123.90
Purchase #5	$56.70	10.162%	$62.4619	$62.46	$62.45	$62.50
Purchase #6	$90.86	13.610%	$103.226	$103.23	$103.25	$103.20
Purchase #7	$239.46	11.304%	$266.5286	$266.53	$266.55	$266.50
7 purchase totals =	$901.41		$983.2885	$983.29	$983.30	$983.30