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	$219.54	9.390%	$240.1548	$240.15	$240.15	$240.20
Purchase #2	$214.47	4.225%	$223.5314	$223.53	$223.55	$223.50
Purchase #3	$34.50	5.491%	$36.3944	$36.39	$36.40	$36.40
Purchase #4	$142.56	6.182%	$151.3731	$151.37	$151.35	$151.40
Purchase #5	$50.26	10.372%	$55.473	$55.47	$55.45	$55.50
Purchase #6	$178.59	12.131%	$200.2548	$200.25	$200.25	$200.30
Purchase #7	$167.54	3.656%	$173.6653	$173.67	$173.65	$173.70
7 purchase totals =	$1,007.46		$1,080.8468	$1,080.83	$1,080.80	$1,081.00