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	$68.65	13.672%	$78.0358	$78.04	$78.05	$78.00
Purchase #2	$24.89	5.392%	$26.2321	$26.23	$26.25	$26.20
Purchase #3	$144.49	4.487%	$150.9733	$150.97	$150.95	$151.00
Purchase #4	$99.75	8.471%	$108.1998	$108.20	$108.20	$108.20
Purchase #5	$220.88	4.824%	$231.5353	$231.54	$231.55	$231.50
Purchase #6	$227.52	10.143%	$250.5974	$250.60	$250.60	$250.60
Purchase #7	$205.76	4.784%	$215.6036	$215.60	$215.60	$215.60
7 purchase totals =	$991.94		$1,061.1773	$1,061.18	$1,061.20	$1,061.10