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	$237.49	11.431%	$264.6375	$264.64	$264.65	$264.60
Purchase #2	$63.77	7.383%	$68.4781	$68.48	$68.50	$68.50
Purchase #3	$51.88	5.622%	$54.7967	$54.80	$54.80	$54.80
Purchase #4	$134.74	11.705%	$150.5113	$150.51	$150.50	$150.50
Purchase #5	$76.45	5.515%	$80.6662	$80.67	$80.65	$80.70
Purchase #6	$86.26	4.662%	$90.2814	$90.28	$90.30	$90.30
Purchase #7	$95.99	10.208%	$105.7887	$105.79	$105.80	$105.80
7 purchase totals =	$746.58		$815.1599	$815.17	$815.20	$815.20