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	$135.68	12.708%	$152.9222	$152.92	$152.90	$152.90
Purchase #2	$92.36	9.694%	$101.3134	$101.31	$101.30	$101.30
Purchase #3	$159.54	13.593%	$181.2263	$181.23	$181.25	$181.20
Purchase #4	$158.66	4.367%	$165.5887	$165.59	$165.60	$165.60
Purchase #5	$63.93	7.377%	$68.6461	$68.65	$68.65	$68.60
Purchase #6	$107.44	5.503%	$113.3524	$113.35	$113.35	$113.40
Purchase #7	$208.64	11.853%	$233.3701	$233.37	$233.35	$233.40
7 purchase totals =	$926.25		$1,016.4192	$1,016.42	$1,016.40	$1,016.40