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	$100.38	5.214%	$105.6138	$105.61	$105.60	$105.60
Purchase #2	$148.39	8.552%	$161.0803	$161.08	$161.10	$161.10
Purchase #3	$95.45	8.631%	$103.6883	$103.69	$103.70	$103.70
Purchase #4	$74.68	11.526%	$83.2876	$83.29	$83.30	$83.30
Purchase #5	$206.90	11.712%	$231.1321	$231.13	$231.15	$231.10
Purchase #6	$216.82	13.186%	$245.4099	$245.41	$245.40	$245.40
Purchase #7	$79.53	11.739%	$88.866	$88.87	$88.85	$88.90
7 purchase totals =	$922.15		$1,019.0780	$1,019.08	$1,019.10	$1,019.10