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	$223.56	11.436%	$249.1263	$249.13	$249.15	$249.10
Purchase #2	$80.49	8.834%	$87.6005	$87.60	$87.60	$87.60
Purchase #3	$43.36	6.491%	$46.1745	$46.17	$46.15	$46.20
Purchase #4	$79.57	12.246%	$89.3141	$89.31	$89.30	$89.30
Purchase #5	$185.86	9.838%	$204.1449	$204.14	$204.15	$204.10
Purchase #6	$161.58	7.339%	$173.4384	$173.44	$173.45	$173.40
Purchase #7	$152.70	12.647%	$172.012	$172.01	$172.00	$172.00
7 purchase totals =	$927.12		$1,021.8107	$1,021.80	$1,021.80	$1,021.70