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	$137.59	9.344%	$150.4464	$150.45	$150.45	$150.40
Purchase #2	$169.46	13.746%	$192.754	$192.75	$192.75	$192.80
Purchase #3	$151.73	7.335%	$162.8594	$162.86	$162.85	$162.90
Purchase #4	$130.42	7.239%	$139.8611	$139.86	$139.85	$139.90
Purchase #5	$16.26	5.813%	$17.2052	$17.21	$17.20	$17.20
Purchase #6	$137.94	9.810%	$151.4719	$151.47	$151.45	$151.50
Purchase #7	$117.32	8.443%	$127.2253	$127.23	$127.25	$127.20
7 purchase totals =	$860.72		$941.8233	$941.83	$941.80	$941.90