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	$65.81	10.128%	$72.4752	$72.48	$72.50	$72.50
Purchase #2	$74.47	9.300%	$81.3957	$81.40	$81.40	$81.40
Purchase #3	$243.82	11.478%	$271.8057	$271.81	$271.80	$271.80
Purchase #4	$173.52	13.332%	$196.6537	$196.65	$196.65	$196.70
Purchase #5	$15.43	5.713%	$16.3115	$16.31	$16.30	$16.30
Purchase #6	$62.25	5.417%	$65.6221	$65.62	$65.60	$65.60
Purchase #7	$233.39	3.307%	$241.1082	$241.11	$241.10	$241.10
7 purchase totals =	$868.69		$945.3721	$945.38	$945.35	$945.40