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	$103.71	13.464%	$117.6735	$117.67	$117.65	$117.70
Purchase #2	$247.62	5.485%	$261.202	$261.20	$261.20	$261.20
Purchase #3	$148.59	8.278%	$160.8903	$160.89	$160.90	$160.90
Purchase #4	$162.83	13.267%	$184.4327	$184.43	$184.45	$184.40
Purchase #5	$200.79	8.245%	$217.3451	$217.35	$217.35	$217.30
Purchase #6	$112.45	13.258%	$127.3586	$127.36	$127.35	$127.40
Purchase #7	$59.60	10.522%	$65.8711	$65.87	$65.85	$65.90
7 purchase totals =	$1,035.59		$1,134.7733	$1,134.77	$1,134.75	$1,134.80