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	$158.29	6.715%	$168.9192	$168.92	$168.90	$168.90
Purchase #2	$172.95	12.326%	$194.2678	$194.27	$194.25	$194.30
Purchase #3	$51.87	6.355%	$55.1663	$55.17	$55.15	$55.20
Purchase #4	$138.65	11.402%	$154.4589	$154.46	$154.45	$154.50
Purchase #5	$94.77	8.254%	$102.5923	$102.59	$102.60	$102.60
Purchase #6	$38.42	13.270%	$43.5183	$43.52	$43.50	$43.50
Purchase #7	$56.27	10.161%	$61.9876	$61.99	$62.00	$62.00
7 purchase totals =	$711.22		$780.9104	$780.92	$780.85	$781.00