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	$117.65	8.434%	$127.5726	$127.57	$127.55	$127.60
Purchase #2	$95.81	11.742%	$107.06	$107.06	$107.05	$107.10
Purchase #3	$196.95	10.784%	$218.1891	$218.19	$218.20	$218.20
Purchase #4	$26.43	13.511%	$30.001	$30.00	$30.00	$30.00
Purchase #5	$208.55	3.314%	$215.4613	$215.46	$215.45	$215.50
Purchase #6	$102.63	8.706%	$111.565	$111.57	$111.55	$111.60
Purchase #7	$55.45	6.810%	$59.2261	$59.23	$59.25	$59.20
7 purchase totals =	$803.47		$869.0751	$869.08	$869.05	$869.20