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	$87.94	3.128%	$90.6908	$90.69	$90.70	$90.70
Purchase #2	$19.95	13.232%	$22.5898	$22.59	$22.60	$22.60
Purchase #3	$19.81	4.620%	$20.7252	$20.73	$20.75	$20.70
Purchase #4	$155.38	10.497%	$171.6902	$171.69	$171.70	$171.70
Purchase #5	$12.33	10.574%	$13.6338	$13.63	$13.65	$13.60
Purchase #6	$119.89	12.579%	$134.971	$134.97	$134.95	$135.00
Purchase #7	$90.90	13.417%	$103.0961	$103.10	$103.10	$103.10
7 purchase totals =	$506.20		$557.3969	$557.40	$557.45	$557.40