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	$200.48	10.627%	$221.785	$221.79	$221.80	$221.80
Purchase #2	$138.25	11.336%	$153.922	$153.92	$153.90	$153.90
Purchase #3	$29.52	10.371%	$32.5815	$32.58	$32.60	$32.60
Purchase #4	$56.29	4.426%	$58.7814	$58.78	$58.80	$58.80
Purchase #5	$94.91	8.405%	$102.8872	$102.89	$102.90	$102.90
Purchase #6	$151.87	13.523%	$172.4074	$172.41	$172.40	$172.40
Purchase #7	$22.40	10.840%	$24.8282	$24.83	$24.85	$24.80
7 purchase totals =	$693.72		$767.1927	$767.20	$767.25	$767.20