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	$111.28	10.791%	$123.2882	$123.29	$123.30	$123.30
Purchase #2	$15.54	10.379%	$17.1529	$17.15	$17.15	$17.20
Purchase #3	$54.71	5.798%	$57.8821	$57.88	$57.90	$57.90
Purchase #4	$170.34	3.237%	$175.8539	$175.85	$175.85	$175.90
Purchase #5	$134.43	6.558%	$143.2459	$143.25	$143.25	$143.20
Purchase #6	$190.50	13.761%	$216.7147	$216.71	$216.70	$216.70
Purchase #7	$26.60	10.443%	$29.3778	$29.38	$29.40	$29.40
7 purchase totals =	$703.40		$763.5155	$763.51	$763.55	$763.60