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	$198.46	10.560%	$219.4174	$219.42	$219.40	$219.40
Purchase #2	$174.36	12.507%	$196.1672	$196.17	$196.15	$196.20
Purchase #3	$22.55	8.697%	$24.5112	$24.51	$24.50	$24.50
Purchase #4	$130.38	13.682%	$148.2186	$148.22	$148.20	$148.20
Purchase #5	$77.45	6.396%	$82.4037	$82.40	$82.40	$82.40
Purchase #6	$15.90	9.679%	$17.439	$17.44	$17.45	$17.40
Purchase #7	$235.37	11.738%	$262.9977	$263.00	$263.00	$263.00
7 purchase totals =	$854.47		$951.1548	$951.16	$951.10	$951.10