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	$99.77	13.466%	$113.205	$113.21	$113.20	$113.20
Purchase #2	$187.82	4.582%	$196.4259	$196.43	$196.45	$196.40
Purchase #3	$117.74	7.665%	$126.7648	$126.76	$126.75	$126.80
Purchase #4	$13.65	4.756%	$14.2992	$14.30	$14.30	$14.30
Purchase #5	$15.59	12.343%	$17.5143	$17.51	$17.50	$17.50
Purchase #6	$106.44	10.337%	$117.4427	$117.44	$117.45	$117.40
Purchase #7	$36.78	12.842%	$41.5033	$41.50	$41.50	$41.50
7 purchase totals =	$577.79		$627.1552	$627.15	$627.15	$627.10