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	$128.47	10.320%	$141.7281	$141.73	$141.75	$141.70
Purchase #2	$86.25	4.534%	$90.1606	$90.16	$90.15	$90.20
Purchase #3	$176.56	11.286%	$196.4866	$196.49	$196.50	$196.50
Purchase #4	$27.80	13.370%	$31.5169	$31.52	$31.50	$31.50
Purchase #5	$192.34	13.228%	$217.7827	$217.78	$217.80	$217.80
Purchase #6	$101.44	9.423%	$110.9987	$111.00	$111.00	$111.00
Purchase #7	$18.73	5.560%	$19.7714	$19.77	$19.75	$19.80
7 purchase totals =	$731.59		$808.4450	$808.45	$808.45	$808.50