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	$39.60	11.518%	$44.1611	$44.16	$44.15	$44.20
Purchase #2	$173.97	13.127%	$196.807	$196.81	$196.80	$196.80
Purchase #3	$130.29	6.292%	$138.4878	$138.49	$138.50	$138.50
Purchase #4	$66.51	7.278%	$71.3506	$71.35	$71.35	$71.40
Purchase #5	$19.91	6.584%	$21.2209	$21.22	$21.20	$21.20
Purchase #6	$158.35	3.805%	$164.3752	$164.38	$164.40	$164.40
Purchase #7	$130.39	11.819%	$145.8008	$145.80	$145.80	$145.80
7 purchase totals =	$719.02		$782.2034	$782.21	$782.20	$782.30