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	$131.56	10.141%	$144.9015	$144.90	$144.90	$144.90
Purchase #2	$167.31	3.301%	$172.8329	$172.83	$172.85	$172.80
Purchase #3	$45.96	5.501%	$48.4883	$48.49	$48.50	$48.50
Purchase #4	$101.65	7.354%	$109.1253	$109.13	$109.15	$109.10
Purchase #5	$134.53	3.622%	$139.4027	$139.40	$139.40	$139.40
Purchase #6	$175.25	6.207%	$186.1278	$186.13	$186.15	$186.10
Purchase #7	$235.50	5.262%	$247.892	$247.89	$247.90	$247.90
7 purchase totals =	$991.76		$1,048.7705	$1,048.77	$1,048.85	$1,048.70