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	$175.38	12.199%	$196.7746	$196.77	$196.75	$196.80
Purchase #2	$108.88	7.393%	$116.9295	$116.93	$116.95	$116.90
Purchase #3	$26.35	8.252%	$28.5244	$28.52	$28.50	$28.50
Purchase #4	$20.96	12.244%	$23.5263	$23.53	$23.55	$23.50
Purchase #5	$15.30	7.341%	$16.4232	$16.42	$16.40	$16.40
Purchase #6	$53.33	10.773%	$59.0752	$59.08	$59.10	$59.10
Purchase #7	$113.96	3.524%	$117.976	$117.98	$118.00	$118.00
7 purchase totals =	$514.16		$559.2292	$559.23	$559.25	$559.20