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	$146.87	8.836%	$159.8474	$159.85	$159.85	$159.80
Purchase #2	$151.46	12.357%	$170.1759	$170.18	$170.20	$170.20
Purchase #3	$179.84	5.376%	$189.5082	$189.51	$189.50	$189.50
Purchase #4	$127.38	9.375%	$139.3219	$139.32	$139.30	$139.30
Purchase #5	$147.83	11.105%	$164.2465	$164.25	$164.25	$164.20
Purchase #6	$130.72	7.442%	$140.4482	$140.45	$140.45	$140.40
Purchase #7	$212.37	4.828%	$222.6232	$222.62	$222.60	$222.60
7 purchase totals =	$1,096.47		$1,186.1713	$1,186.18	$1,186.15	$1,186.00