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	$72.28	4.743%	$75.7082	$75.71	$75.70	$75.70
Purchase #2	$156.71	5.690%	$165.6268	$165.63	$165.65	$165.60
Purchase #3	$217.54	11.722%	$243.04	$243.04	$243.05	$243.00
Purchase #4	$114.42	11.426%	$127.4936	$127.49	$127.50	$127.50
Purchase #5	$107.51	11.569%	$119.9478	$119.95	$119.95	$119.90
Purchase #6	$16.94	13.294%	$19.192	$19.19	$19.20	$19.20
Purchase #7	$205.65	10.648%	$227.5476	$227.55	$227.55	$227.50
7 purchase totals =	$891.05		$978.5560	$978.56	$978.60	$978.40