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	$64.89	9.331%	$70.9449	$70.94	$70.95	$70.90
Purchase #2	$162.45	6.113%	$172.3806	$172.38	$172.40	$172.40
Purchase #3	$176.59	7.760%	$190.2934	$190.29	$190.30	$190.30
Purchase #4	$154.81	10.151%	$170.5248	$170.52	$170.50	$170.50
Purchase #5	$11.63	10.704%	$12.8749	$12.87	$12.85	$12.90
Purchase #6	$30.25	4.406%	$31.5828	$31.58	$31.60	$31.60
Purchase #7	$132.55	11.250%	$147.4619	$147.46	$147.45	$147.50
7 purchase totals =	$733.17		$796.0633	$796.04	$796.05	$796.10