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	$158.99	9.546%	$174.1672	$174.17	$174.15	$174.20
Purchase #2	$44.94	7.153%	$48.1546	$48.15	$48.15	$48.20
Purchase #3	$10.65	11.482%	$11.8728	$11.87	$11.85	$11.90
Purchase #4	$96.48	9.469%	$105.6157	$105.62	$105.60	$105.60
Purchase #5	$29.46	13.232%	$33.3581	$33.36	$33.35	$33.40
Purchase #6	$33.94	3.499%	$35.1276	$35.13	$35.15	$35.10
Purchase #7	$48.52	10.278%	$53.5069	$53.51	$53.50	$53.50
7 purchase totals =	$422.98		$461.8029	$461.81	$461.75	$461.90