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	$42.87	12.377%	$48.176	$48.18	$48.20	$48.20
Purchase #2	$30.55	7.420%	$32.8168	$32.82	$32.80	$32.80
Purchase #3	$79.34	13.270%	$89.8684	$89.87	$89.85	$89.90
Purchase #4	$34.58	10.432%	$38.1874	$38.19	$38.20	$38.20
Purchase #5	$80.87	12.701%	$91.1413	$91.14	$91.15	$91.10
Purchase #6	$118.78	11.631%	$132.5953	$132.60	$132.60	$132.60
Purchase #7	$238.46	10.491%	$263.4768	$263.48	$263.50	$263.50
7 purchase totals =	$625.45		$696.2620	$696.28	$696.30	$696.30