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	$127.35	13.465%	$144.4977	$144.50	$144.50	$144.50
Purchase #2	$199.85	11.182%	$222.1972	$222.20	$222.20	$222.20
Purchase #3	$202.34	9.314%	$221.1859	$221.19	$221.20	$221.20
Purchase #4	$188.88	13.354%	$214.103	$214.10	$214.10	$214.10
Purchase #5	$198.43	9.243%	$216.7709	$216.77	$216.75	$216.80
Purchase #6	$45.27	8.426%	$49.0845	$49.08	$49.10	$49.10
Purchase #7	$179.69	9.503%	$196.7659	$196.77	$196.75	$196.80
7 purchase totals =	$1,141.81		$1,264.6051	$1,264.61	$1,264.60	$1,264.70