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	$149.55	4.470%	$156.2349	$156.23	$156.25	$156.20
Purchase #2	$49.83	11.691%	$55.6556	$55.66	$55.65	$55.70
Purchase #3	$99.81	6.376%	$106.1739	$106.17	$106.15	$106.20
Purchase #4	$48.47	8.691%	$52.6825	$52.68	$52.70	$52.70
Purchase #5	$116.36	9.324%	$127.2094	$127.21	$127.20	$127.20
Purchase #6	$188.50	13.168%	$213.3217	$213.32	$213.30	$213.30
Purchase #7	$197.25	12.658%	$222.2179	$222.22	$222.20	$222.20
7 purchase totals =	$849.77		$933.4959	$933.49	$933.45	$933.50