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	$12.59	11.360%	$14.0202	$14.02	$14.00	$14.00
Purchase #2	$188.86	5.693%	$199.6118	$199.61	$199.60	$199.60
Purchase #3	$107.80	3.740%	$111.8317	$111.83	$111.85	$111.80
Purchase #4	$87.49	13.584%	$99.3746	$99.37	$99.35	$99.40
Purchase #5	$242.42	4.695%	$253.8016	$253.80	$253.80	$253.80
Purchase #6	$13.97	13.500%	$15.856	$15.86	$15.85	$15.90
Purchase #7	$106.66	13.800%	$121.3791	$121.38	$121.40	$121.40
7 purchase totals =	$759.79		$815.8750	$815.87	$815.85	$815.90