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	$136.41	11.162%	$151.6361	$151.64	$151.65	$151.60
Purchase #2	$190.28	10.442%	$210.149	$210.15	$210.15	$210.10
Purchase #3	$28.34	9.563%	$31.0502	$31.05	$31.05	$31.10
Purchase #4	$104.47	13.392%	$118.4606	$118.46	$118.45	$118.50
Purchase #5	$14.48	12.156%	$16.2402	$16.24	$16.25	$16.20
Purchase #6	$144.85	5.669%	$153.0615	$153.06	$153.05	$153.10
Purchase #7	$100.35	13.518%	$113.9153	$113.92	$113.90	$113.90
7 purchase totals =	$719.18		$794.5129	$794.52	$794.50	$794.50