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	$39.94	10.472%	$44.1225	$44.12	$44.10	$44.10
Purchase #2	$63.40	4.339%	$66.1509	$66.15	$66.15	$66.20
Purchase #3	$105.33	4.551%	$110.1236	$110.12	$110.10	$110.10
Purchase #4	$83.75	7.141%	$89.7306	$89.73	$89.75	$89.70
Purchase #5	$248.73	10.216%	$274.1403	$274.14	$274.15	$274.10
Purchase #6	$154.45	5.340%	$162.6976	$162.70	$162.70	$162.70
Purchase #7	$111.74	10.648%	$123.6381	$123.64	$123.65	$123.60
7 purchase totals =	$807.34		$870.6036	$870.60	$870.60	$870.50