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	$197.88	9.349%	$216.3798	$216.38	$216.40	$216.40
Purchase #2	$16.32	11.724%	$18.2334	$18.23	$18.25	$18.20
Purchase #3	$29.59	8.235%	$32.0267	$32.03	$32.05	$32.00
Purchase #4	$88.88	11.769%	$99.3403	$99.34	$99.35	$99.30
Purchase #5	$128.95	3.430%	$133.373	$133.37	$133.35	$133.40
Purchase #6	$85.63	5.852%	$90.6411	$90.64	$90.65	$90.60
Purchase #7	$34.51	11.353%	$38.4279	$38.43	$38.45	$38.40
7 purchase totals =	$581.76		$628.4222	$628.42	$628.50	$628.30