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	$219.41	12.719%	$247.3168	$247.32	$247.30	$247.30
Purchase #2	$104.65	11.179%	$116.3488	$116.35	$116.35	$116.30
Purchase #3	$112.65	13.308%	$127.6415	$127.64	$127.65	$127.60
Purchase #4	$97.68	5.499%	$103.0514	$103.05	$103.05	$103.10
Purchase #5	$141.87	11.671%	$158.4276	$158.43	$158.45	$158.40
Purchase #6	$136.75	9.754%	$150.0886	$150.09	$150.10	$150.10
Purchase #7	$21.86	10.255%	$24.1017	$24.10	$24.10	$24.10
7 purchase totals =	$834.87		$926.9764	$926.98	$927.00	$926.90