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	$173.96	4.433%	$181.6716	$181.67	$181.65	$181.70
Purchase #2	$89.35	12.656%	$100.6581	$100.66	$100.65	$100.70
Purchase #3	$165.78	5.644%	$175.1366	$175.14	$175.15	$175.10
Purchase #4	$116.47	9.440%	$127.4648	$127.46	$127.45	$127.50
Purchase #5	$16.97	9.509%	$18.5837	$18.58	$18.60	$18.60
Purchase #6	$159.73	6.117%	$169.5007	$169.50	$169.50	$169.50
Purchase #7	$78.76	12.172%	$88.3467	$88.35	$88.35	$88.30
7 purchase totals =	$801.02		$861.3622	$861.36	$861.35	$861.40