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	$192.94	13.842%	$219.6468	$219.65	$219.65	$219.60
Purchase #2	$229.30	12.790%	$258.6275	$258.63	$258.65	$258.60
Purchase #3	$222.90	4.764%	$233.519	$233.52	$233.50	$233.50
Purchase #4	$137.37	6.700%	$146.5738	$146.57	$146.55	$146.60
Purchase #5	$13.82	6.378%	$14.7014	$14.70	$14.70	$14.70
Purchase #6	$141.81	5.328%	$149.3656	$149.37	$149.35	$149.40
Purchase #7	$95.52	10.363%	$105.4187	$105.42	$105.40	$105.40
7 purchase totals =	$1,033.66		$1,127.8528	$1,127.86	$1,127.80	$1,127.80