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	$100.29	11.852%	$112.1764	$112.18	$112.20	$112.20
Purchase #2	$89.55	12.233%	$100.5047	$100.50	$100.50	$100.50
Purchase #3	$50.93	5.244%	$53.6008	$53.60	$53.60	$53.60
Purchase #4	$95.50	11.769%	$106.7394	$106.74	$106.75	$106.70
Purchase #5	$145.88	13.742%	$165.9268	$165.93	$165.95	$165.90
Purchase #6	$234.68	10.336%	$258.9365	$258.94	$258.95	$258.90
Purchase #7	$196.31	9.183%	$214.3371	$214.34	$214.35	$214.30
7 purchase totals =	$913.14		$1,012.2217	$1,012.23	$1,012.30	$1,012.10