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	$234.72	12.273%	$263.5272	$263.53	$263.55	$263.50
Purchase #2	$18.53	6.745%	$19.7798	$19.78	$19.80	$19.80
Purchase #3	$42.32	4.784%	$44.3446	$44.34	$44.35	$44.30
Purchase #4	$231.38	9.180%	$252.6207	$252.62	$252.60	$252.60
Purchase #5	$10.68	13.600%	$12.1325	$12.13	$12.15	$12.10
Purchase #6	$134.43	8.239%	$145.5057	$145.51	$145.50	$145.50
Purchase #7	$98.83	12.629%	$111.3112	$111.31	$111.30	$111.30
7 purchase totals =	$770.89		$849.2217	$849.22	$849.25	$849.10