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	$116.45	11.663%	$130.0316	$130.03	$130.05	$130.00
Purchase #2	$53.43	7.379%	$57.3726	$57.37	$57.35	$57.40
Purchase #3	$95.71	4.397%	$99.9184	$99.92	$99.90	$99.90
Purchase #4	$91.60	11.136%	$101.8006	$101.80	$101.80	$101.80
Purchase #5	$26.32	3.538%	$27.2512	$27.25	$27.25	$27.30
Purchase #6	$15.76	9.465%	$17.2517	$17.25	$17.25	$17.30
Purchase #7	$64.59	12.748%	$72.8239	$72.82	$72.80	$72.80
7 purchase totals =	$463.86		$506.4500	$506.44	$506.40	$506.50