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	$133.49	9.762%	$146.5213	$146.52	$146.50	$146.50
Purchase #2	$176.27	5.790%	$186.476	$186.48	$186.50	$186.50
Purchase #3	$237.50	3.124%	$244.9195	$244.92	$244.90	$244.90
Purchase #4	$58.85	12.296%	$66.0862	$66.09	$66.10	$66.10
Purchase #5	$151.41	9.226%	$165.3791	$165.38	$165.40	$165.40
Purchase #6	$140.59	3.724%	$145.8256	$145.83	$145.85	$145.80
Purchase #7	$56.67	8.736%	$61.6207	$61.62	$61.60	$61.60
7 purchase totals =	$954.78		$1,016.8284	$1,016.84	$1,016.85	$1,016.80