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	$171.49	10.256%	$189.078	$189.08	$189.10	$189.10
Purchase #2	$186.76	13.435%	$211.8512	$211.85	$211.85	$211.90
Purchase #3	$121.48	5.188%	$127.7824	$127.78	$127.80	$127.80
Purchase #4	$122.62	3.602%	$127.0368	$127.04	$127.05	$127.00
Purchase #5	$97.66	5.820%	$103.3438	$103.34	$103.35	$103.30
Purchase #6	$57.84	13.424%	$65.6044	$65.60	$65.60	$65.60
Purchase #7	$177.28	7.426%	$190.4448	$190.44	$190.45	$190.40
7 purchase totals =	$935.13		$1,015.1414	$1,015.13	$1,015.20	$1,015.10