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	$238.83	3.264%	$246.6254	$246.63	$246.65	$246.60
Purchase #2	$63.61	3.635%	$65.9222	$65.92	$65.90	$65.90
Purchase #3	$117.85	10.458%	$130.1748	$130.17	$130.15	$130.20
Purchase #4	$159.59	4.338%	$166.513	$166.51	$166.50	$166.50
Purchase #5	$98.52	6.497%	$104.9208	$104.92	$104.90	$104.90
Purchase #6	$49.45	13.592%	$56.1712	$56.17	$56.15	$56.20
Purchase #7	$66.85	13.535%	$75.8981	$75.90	$75.90	$75.90
7 purchase totals =	$794.70		$846.2255	$846.22	$846.15	$846.20