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	$134.31	7.324%	$144.1469	$144.15	$144.15	$144.10
Purchase #2	$60.56	6.397%	$64.434	$64.43	$64.45	$64.40
Purchase #3	$224.89	9.783%	$246.891	$246.89	$246.90	$246.90
Purchase #4	$174.63	10.516%	$192.9941	$192.99	$193.00	$193.00
Purchase #5	$29.31	7.830%	$31.605	$31.61	$31.60	$31.60
Purchase #6	$199.72	4.163%	$208.0343	$208.03	$208.05	$208.00
Purchase #7	$116.56	9.391%	$127.5061	$127.51	$127.50	$127.50
7 purchase totals =	$939.98		$1,015.6114	$1,015.61	$1,015.65	$1,015.50