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	$211.76	12.719%	$238.6938	$238.69	$238.70	$238.70
Purchase #2	$34.28	7.556%	$36.8702	$36.87	$36.85	$36.90
Purchase #3	$207.60	10.222%	$228.8209	$228.82	$228.80	$228.80
Purchase #4	$37.40	7.387%	$40.1627	$40.16	$40.15	$40.20
Purchase #5	$208.77	3.266%	$215.5884	$215.59	$215.60	$215.60
Purchase #6	$69.42	4.517%	$72.5557	$72.56	$72.55	$72.60
Purchase #7	$229.67	7.327%	$246.4979	$246.50	$246.50	$246.50
7 purchase totals =	$998.90		$1,079.1896	$1,079.19	$1,079.15	$1,079.30