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	$144.82	5.693%	$153.0646	$153.06	$153.05	$153.10
Purchase #2	$45.95	11.332%	$51.1571	$51.16	$51.15	$51.20
Purchase #3	$146.59	3.508%	$151.7324	$151.73	$151.75	$151.70
Purchase #4	$210.53	8.672%	$228.7872	$228.79	$228.80	$228.80
Purchase #5	$75.25	13.850%	$85.6721	$85.67	$85.65	$85.70
Purchase #6	$168.92	3.737%	$175.2325	$175.23	$175.25	$175.20
Purchase #7	$146.54	5.239%	$154.2172	$154.22	$154.20	$154.20
7 purchase totals =	$938.60		$999.8631	$999.86	$999.85	$999.90