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	$204.37	8.873%	$222.5038	$222.50	$222.50	$222.50
Purchase #2	$118.65	4.252%	$123.695	$123.70	$123.70	$123.70
Purchase #3	$96.63	10.541%	$106.8158	$106.82	$106.80	$106.80
Purchase #4	$73.30	11.292%	$81.577	$81.58	$81.60	$81.60
Purchase #5	$250.94	5.472%	$264.6714	$264.67	$264.65	$264.70
Purchase #6	$132.60	3.398%	$137.1057	$137.11	$137.10	$137.10
Purchase #7	$150.57	6.491%	$160.3435	$160.34	$160.35	$160.30
7 purchase totals =	$1,027.06		$1,096.7122	$1,096.72	$1,096.70	$1,096.70