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	$141.37	12.844%	$159.5276	$159.53	$159.55	$159.50
Purchase #2	$167.32	5.193%	$176.0089	$176.01	$176.00	$176.00
Purchase #3	$185.88	13.472%	$210.9218	$210.92	$210.90	$210.90
Purchase #4	$38.54	12.244%	$43.2588	$43.26	$43.25	$43.30
Purchase #5	$233.72	9.157%	$255.1217	$255.12	$255.10	$255.10
Purchase #6	$234.61	7.793%	$252.8932	$252.89	$252.90	$252.90
Purchase #7	$198.59	10.736%	$219.9106	$219.91	$219.90	$219.90
7 purchase totals =	$1,200.03		$1,317.6426	$1,317.64	$1,317.60	$1,317.60