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	$133.48	8.316%	$144.5802	$144.58	$144.60	$144.60
Purchase #2	$51.51	9.736%	$56.525	$56.53	$56.55	$56.50
Purchase #3	$75.58	10.378%	$83.4237	$83.42	$83.40	$83.40
Purchase #4	$32.97	3.546%	$34.1391	$34.14	$34.15	$34.10
Purchase #5	$160.75	9.861%	$176.6016	$176.60	$176.60	$176.60
Purchase #6	$156.98	6.447%	$167.1005	$167.10	$167.10	$167.10
Purchase #7	$90.39	9.592%	$99.0602	$99.06	$99.05	$99.10
7 purchase totals =	$701.66		$761.4303	$761.43	$761.45	$761.40