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	$15.38	12.837%	$17.3543	$17.35	$17.35	$17.40
Purchase #2	$43.42	11.672%	$48.488	$48.49	$48.50	$48.50
Purchase #3	$99.59	11.619%	$111.1614	$111.16	$111.15	$111.20
Purchase #4	$127.59	7.799%	$137.5407	$137.54	$137.55	$137.50
Purchase #5	$112.80	3.236%	$116.4502	$116.45	$116.45	$116.50
Purchase #6	$71.72	3.497%	$74.228	$74.23	$74.25	$74.20
Purchase #7	$82.88	4.873%	$86.9187	$86.92	$86.90	$86.90
7 purchase totals =	$553.38		$592.1413	$592.14	$592.15	$592.20