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	$105.52	12.410%	$118.615	$118.62	$118.60	$118.60
Purchase #2	$76.31	7.622%	$82.1263	$82.13	$82.15	$82.10
Purchase #3	$167.45	5.375%	$176.4504	$176.45	$176.45	$176.50
Purchase #4	$238.86	5.349%	$251.6366	$251.64	$251.65	$251.60
Purchase #5	$217.98	11.554%	$243.1654	$243.17	$243.15	$243.20
Purchase #6	$71.75	13.404%	$81.3674	$81.37	$81.35	$81.40
Purchase #7	$146.45	6.177%	$155.4962	$155.50	$155.50	$155.50
7 purchase totals =	$1,024.32		$1,108.8573	$1,108.88	$1,108.85	$1,108.90