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	$243.70	5.205%	$256.3846	$256.38	$256.40	$256.40
Purchase #2	$62.81	6.294%	$66.7633	$66.76	$66.75	$66.80
Purchase #3	$223.53	4.854%	$234.3801	$234.38	$234.40	$234.40
Purchase #4	$29.27	10.651%	$32.3875	$32.39	$32.40	$32.40
Purchase #5	$12.35	9.817%	$13.5624	$13.56	$13.55	$13.60
Purchase #6	$235.83	7.476%	$253.4607	$253.46	$253.45	$253.50
Purchase #7	$180.96	3.339%	$187.0023	$187.00	$187.00	$187.00
7 purchase totals =	$988.45		$1,043.9409	$1,043.93	$1,043.95	$1,044.10