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	$86.76	3.189%	$89.5268	$89.53	$89.55	$89.50
Purchase #2	$9.80	10.808%	$10.8592	$10.86	$10.85	$10.90
Purchase #3	$216.86	12.826%	$244.6745	$244.67	$244.65	$244.70
Purchase #4	$23.72	11.422%	$26.4293	$26.43	$26.45	$26.40
Purchase #5	$109.27	4.478%	$114.1631	$114.16	$114.15	$114.20
Purchase #6	$67.40	13.593%	$76.5617	$76.56	$76.55	$76.60
Purchase #7	$76.59	7.784%	$82.5518	$82.55	$82.55	$82.60
7 purchase totals =	$590.40		$644.7664	$644.76	$644.75	$644.90