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	$31.32	13.826%	$35.6503	$35.65	$35.65	$35.70
Purchase #2	$152.51	11.688%	$170.3354	$170.34	$170.35	$170.30
Purchase #3	$115.97	10.810%	$128.5064	$128.51	$128.50	$128.50
Purchase #4	$167.61	13.551%	$190.3228	$190.32	$190.30	$190.30
Purchase #5	$21.83	10.758%	$24.1785	$24.18	$24.20	$24.20
Purchase #6	$33.65	10.397%	$37.1486	$37.15	$37.15	$37.10
Purchase #7	$33.82	5.233%	$35.5898	$35.59	$35.60	$35.60
7 purchase totals =	$556.71		$621.7318	$621.74	$621.75	$621.70