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	$152.61	12.191%	$171.2147	$171.21	$171.20	$171.20
Purchase #2	$46.76	13.634%	$53.1353	$53.14	$53.15	$53.10
Purchase #3	$49.59	5.320%	$52.2282	$52.23	$52.25	$52.20
Purchase #4	$38.50	5.230%	$40.5136	$40.51	$40.50	$40.50
Purchase #5	$95.66	13.377%	$108.4564	$108.46	$108.45	$108.50
Purchase #6	$40.88	9.642%	$44.8216	$44.82	$44.80	$44.80
Purchase #7	$144.56	11.849%	$161.6889	$161.69	$161.70	$161.70
7 purchase totals =	$568.56		$632.0587	$632.06	$632.05	$632.00