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	$33.90	12.179%	$38.0287	$38.03	$38.05	$38.00
Purchase #2	$248.36	5.486%	$261.985	$261.99	$262.00	$262.00
Purchase #3	$49.81	11.300%	$55.4385	$55.44	$55.45	$55.40
Purchase #4	$78.49	13.241%	$88.8829	$88.88	$88.90	$88.90
Purchase #5	$181.27	6.133%	$192.3873	$192.39	$192.40	$192.40
Purchase #6	$89.39	6.382%	$95.0949	$95.09	$95.10	$95.10
Purchase #7	$60.82	6.238%	$64.614	$64.61	$64.60	$64.60
7 purchase totals =	$742.04		$796.4313	$796.43	$796.50	$796.40