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	$77.96	5.245%	$82.049	$82.05	$82.05	$82.00
Purchase #2	$114.74	13.450%	$130.1725	$130.17	$130.15	$130.20
Purchase #3	$37.58	6.357%	$39.969	$39.97	$39.95	$40.00
Purchase #4	$99.89	11.217%	$111.0947	$111.09	$111.10	$111.10
Purchase #5	$170.50	7.420%	$183.1511	$183.15	$183.15	$183.20
Purchase #6	$28.28	3.733%	$29.3357	$29.34	$29.35	$29.30
Purchase #7	$180.60	6.766%	$192.8194	$192.82	$192.80	$192.80
7 purchase totals =	$709.55		$768.5914	$768.59	$768.55	$768.60