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	$114.62	13.764%	$130.3963	$130.40	$130.40	$130.40
Purchase #2	$54.78	7.863%	$59.0874	$59.09	$59.10	$59.10
Purchase #3	$117.66	10.803%	$130.3708	$130.37	$130.35	$130.40
Purchase #4	$43.33	4.301%	$45.1936	$45.19	$45.20	$45.20
Purchase #5	$152.31	5.818%	$161.1714	$161.17	$161.15	$161.20
Purchase #6	$96.41	4.342%	$100.5961	$100.60	$100.60	$100.60
Purchase #7	$36.96	3.679%	$38.3198	$38.32	$38.30	$38.30
7 purchase totals =	$616.07		$665.1354	$665.14	$665.10	$665.20