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	$135.63	5.720%	$143.388	$143.39	$143.40	$143.40
Purchase #2	$15.84	10.870%	$17.5618	$17.56	$17.55	$17.60
Purchase #3	$234.45	8.858%	$255.2176	$255.22	$255.20	$255.20
Purchase #4	$110.75	11.273%	$123.2348	$123.23	$123.25	$123.20
Purchase #5	$230.91	8.445%	$250.4103	$250.41	$250.40	$250.40
Purchase #6	$93.93	3.852%	$97.5482	$97.55	$97.55	$97.50
Purchase #7	$176.38	10.305%	$194.556	$194.56	$194.55	$194.60
7 purchase totals =	$997.89		$1,081.9167	$1,081.92	$1,081.90	$1,081.90