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	$73.56	4.540%	$76.8996	$76.90	$76.90	$76.90
Purchase #2	$78.58	5.387%	$82.8131	$82.81	$82.80	$82.80
Purchase #3	$183.87	13.632%	$208.9352	$208.94	$208.95	$208.90
Purchase #4	$136.49	12.613%	$153.7055	$153.71	$153.70	$153.70
Purchase #5	$106.81	4.665%	$111.7927	$111.79	$111.80	$111.80
Purchase #6	$90.42	13.292%	$102.4386	$102.44	$102.45	$102.40
Purchase #7	$163.71	12.467%	$184.1197	$184.12	$184.10	$184.10
7 purchase totals =	$833.44		$920.7044	$920.71	$920.70	$920.60