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	$95.72	10.301%	$105.5801	$105.58	$105.60	$105.60
Purchase #2	$122.67	10.452%	$135.4915	$135.49	$135.50	$135.50
Purchase #3	$172.61	4.789%	$180.8763	$180.88	$180.90	$180.90
Purchase #4	$158.66	6.786%	$169.4267	$169.43	$169.45	$169.40
Purchase #5	$181.80	3.567%	$188.2848	$188.28	$188.30	$188.30
Purchase #6	$158.57	9.159%	$173.0934	$173.09	$173.10	$173.10
Purchase #7	$105.38	7.607%	$113.3963	$113.40	$113.40	$113.40
7 purchase totals =	$995.41		$1,066.1491	$1,066.15	$1,066.25	$1,066.20