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	$247.42	9.233%	$270.2643	$270.26	$270.25	$270.30
Purchase #2	$134.65	5.327%	$141.8228	$141.82	$141.80	$141.80
Purchase #3	$167.96	11.589%	$187.4249	$187.42	$187.40	$187.40
Purchase #4	$147.44	4.161%	$153.575	$153.58	$153.60	$153.60
Purchase #5	$27.92	13.423%	$31.6677	$31.67	$31.65	$31.70
Purchase #6	$222.75	12.102%	$249.7072	$249.71	$249.70	$249.70
Purchase #7	$19.77	3.339%	$20.4301	$20.43	$20.45	$20.40
7 purchase totals =	$967.91		$1,054.8920	$1,054.89	$1,054.85	$1,054.90