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	$14.55	3.632%	$15.0785	$15.08	$15.10	$15.10
Purchase #2	$75.77	10.579%	$83.7857	$83.79	$83.80	$83.80
Purchase #3	$90.51	9.688%	$99.2786	$99.28	$99.30	$99.30
Purchase #4	$118.49	4.761%	$124.1313	$124.13	$124.15	$124.10
Purchase #5	$116.56	6.497%	$124.1329	$124.13	$124.15	$124.10
Purchase #6	$141.96	11.244%	$157.922	$157.92	$157.90	$157.90
Purchase #7	$118.82	8.223%	$128.5906	$128.59	$128.60	$128.60
7 purchase totals =	$676.66		$732.9196	$732.92	$733.00	$732.90