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	$55.82	10.824%	$61.862	$61.86	$61.85	$61.90
Purchase #2	$49.99	3.282%	$51.6307	$51.63	$51.65	$51.60
Purchase #3	$65.85	13.289%	$74.6008	$74.60	$74.60	$74.60
Purchase #4	$35.79	10.796%	$39.6539	$39.65	$39.65	$39.70
Purchase #5	$141.97	5.311%	$149.51	$149.51	$149.50	$149.50
Purchase #6	$103.44	7.621%	$111.3232	$111.32	$111.30	$111.30
Purchase #7	$111.44	11.796%	$124.5855	$124.59	$124.60	$124.60
7 purchase totals =	$564.30		$613.1661	$613.16	$613.15	$613.20