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	$64.71	11.495%	$72.1484	$72.15	$72.15	$72.10
Purchase #2	$44.40	11.750%	$49.617	$49.62	$49.60	$49.60
Purchase #3	$49.26	11.296%	$54.8244	$54.82	$54.80	$54.80
Purchase #4	$220.61	8.107%	$238.4949	$238.49	$238.50	$238.50
Purchase #5	$154.37	4.648%	$161.5451	$161.55	$161.55	$161.50
Purchase #6	$161.45	3.524%	$167.1395	$167.14	$167.15	$167.10
Purchase #7	$136.71	8.628%	$148.5053	$148.51	$148.50	$148.50
7 purchase totals =	$831.51		$892.2746	$892.28	$892.25	$892.10