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	$118.75	7.181%	$127.2774	$127.28	$127.30	$127.30
Purchase #2	$19.54	8.314%	$21.1646	$21.16	$21.15	$21.20
Purchase #3	$18.31	6.686%	$19.5342	$19.53	$19.55	$19.50
Purchase #4	$16.26	12.244%	$18.2509	$18.25	$18.25	$18.30
Purchase #5	$32.93	5.476%	$34.7332	$34.73	$34.75	$34.70
Purchase #6	$56.84	10.759%	$62.9554	$62.96	$62.95	$63.00
Purchase #7	$243.86	12.849%	$275.1936	$275.19	$275.20	$275.20
7 purchase totals =	$506.49		$559.1093	$559.10	$559.15	$559.20