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	$172.29	12.544%	$193.9021	$193.90	$193.90	$193.90
Purchase #2	$37.94	6.166%	$40.2794	$40.28	$40.30	$40.30
Purchase #3	$151.50	9.418%	$165.7683	$165.77	$165.75	$165.80
Purchase #4	$196.47	10.527%	$217.1524	$217.15	$217.15	$217.20
Purchase #5	$167.58	11.606%	$187.0293	$187.03	$187.05	$187.00
Purchase #6	$81.86	6.787%	$87.4158	$87.42	$87.40	$87.40
Purchase #7	$156.63	10.194%	$172.5969	$172.60	$172.60	$172.60
7 purchase totals =	$964.27		$1,064.1442	$1,064.15	$1,064.15	$1,064.20