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	$222.71	8.615%	$241.8965	$241.90	$241.90	$241.90
Purchase #2	$20.38	5.263%	$21.4526	$21.45	$21.45	$21.50
Purchase #3	$70.53	11.227%	$78.4484	$78.45	$78.45	$78.40
Purchase #4	$75.64	13.153%	$85.5889	$85.59	$85.60	$85.60
Purchase #5	$120.52	11.338%	$134.1846	$134.18	$134.20	$134.20
Purchase #6	$75.63	12.668%	$85.2108	$85.21	$85.20	$85.20
Purchase #7	$162.49	10.861%	$180.138	$180.14	$180.15	$180.10
7 purchase totals =	$747.90		$826.9198	$826.92	$826.95	$826.90