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	$111.39	11.726%	$124.4516	$124.45	$124.45	$124.50
Purchase #2	$82.25	4.464%	$85.9216	$85.92	$85.90	$85.90
Purchase #3	$238.67	7.332%	$256.1693	$256.17	$256.15	$256.20
Purchase #4	$15.31	12.258%	$17.1867	$17.19	$17.20	$17.20
Purchase #5	$167.83	11.791%	$187.6188	$187.62	$187.60	$187.60
Purchase #6	$215.77	8.188%	$233.4372	$233.44	$233.45	$233.40
Purchase #7	$107.95	6.222%	$114.6666	$114.67	$114.65	$114.70
7 purchase totals =	$939.17		$1,019.4518	$1,019.46	$1,019.40	$1,019.50