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	$74.95	4.663%	$78.4449	$78.44	$78.45	$78.40
Purchase #2	$214.48	12.622%	$241.5517	$241.55	$241.55	$241.60
Purchase #3	$152.30	13.498%	$172.8575	$172.86	$172.85	$172.90
Purchase #4	$84.45	6.540%	$89.973	$89.97	$89.95	$90.00
Purchase #5	$44.78	8.397%	$48.5402	$48.54	$48.55	$48.50
Purchase #6	$35.97	13.759%	$40.9191	$40.92	$40.90	$40.90
Purchase #7	$21.75	4.311%	$22.6876	$22.69	$22.70	$22.70
7 purchase totals =	$628.68		$694.9740	$694.97	$694.95	$695.00