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	$94.88	6.222%	$100.7834	$100.78	$100.80	$100.80
Purchase #2	$111.97	4.683%	$117.2136	$117.21	$117.20	$117.20
Purchase #3	$87.44	9.232%	$95.5125	$95.51	$95.50	$95.50
Purchase #4	$160.68	3.593%	$166.4532	$166.45	$166.45	$166.50
Purchase #5	$98.82	9.713%	$108.4184	$108.42	$108.40	$108.40
Purchase #6	$164.66	4.739%	$172.4632	$172.46	$172.45	$172.50
Purchase #7	$177.99	3.589%	$184.3781	$184.38	$184.40	$184.40
7 purchase totals =	$896.44		$945.2224	$945.21	$945.20	$945.30