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	$61.34	10.180%	$67.5844	$67.58	$67.60	$67.60
Purchase #2	$145.98	8.754%	$158.7591	$158.76	$158.75	$158.80
Purchase #3	$99.61	7.363%	$106.9443	$106.94	$106.95	$106.90
Purchase #4	$69.52	13.450%	$78.8704	$78.87	$78.85	$78.90
Purchase #5	$96.62	5.332%	$101.7718	$101.77	$101.75	$101.80
Purchase #6	$65.76	9.306%	$71.8796	$71.88	$71.90	$71.90
Purchase #7	$218.88	5.201%	$230.2639	$230.26	$230.25	$230.30
7 purchase totals =	$757.71		$816.0735	$816.06	$816.05	$816.20