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	$215.45	12.376%	$242.1141	$242.11	$242.10	$242.10
Purchase #2	$64.69	4.588%	$67.658	$67.66	$67.65	$67.70
Purchase #3	$106.60	4.255%	$111.1358	$111.14	$111.15	$111.10
Purchase #4	$114.38	10.365%	$126.2355	$126.24	$126.25	$126.20
Purchase #5	$36.46	4.249%	$38.0092	$38.01	$38.00	$38.00
Purchase #6	$136.77	6.777%	$146.0389	$146.04	$146.05	$146.00
Purchase #7	$31.65	3.107%	$32.6334	$32.63	$32.65	$32.60
7 purchase totals =	$706.00		$763.8249	$763.83	$763.85	$763.70