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	$213.39	5.716%	$225.5874	$225.59	$225.60	$225.60
Purchase #2	$62.56	6.254%	$66.4725	$66.47	$66.45	$66.50
Purchase #3	$143.38	11.725%	$160.1913	$160.19	$160.20	$160.20
Purchase #4	$64.92	11.246%	$72.2209	$72.22	$72.20	$72.20
Purchase #5	$12.59	12.457%	$14.1583	$14.16	$14.15	$14.20
Purchase #6	$43.63	12.356%	$49.0209	$49.02	$49.00	$49.00
Purchase #7	$21.73	5.207%	$22.8615	$22.86	$22.85	$22.90
7 purchase totals =	$562.20		$610.5128	$610.51	$610.45	$610.60