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	$82.29	12.513%	$92.5869	$92.59	$92.60	$92.60
Purchase #2	$45.45	5.777%	$48.0756	$48.08	$48.10	$48.10
Purchase #3	$208.28	8.479%	$225.9401	$225.94	$225.95	$225.90
Purchase #4	$158.30	12.471%	$178.0416	$178.04	$178.05	$178.00
Purchase #5	$132.57	7.506%	$142.5207	$142.52	$142.50	$142.50
Purchase #6	$36.43	7.688%	$39.2307	$39.23	$39.25	$39.20
Purchase #7	$36.43	11.186%	$40.5051	$40.51	$40.50	$40.50
7 purchase totals =	$699.75		$766.9007	$766.91	$766.95	$766.80