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	$134.77	6.805%	$143.9411	$143.94	$143.95	$143.90
Purchase #2	$126.91	7.287%	$136.1579	$136.16	$136.15	$136.20
Purchase #3	$114.59	11.635%	$127.9225	$127.92	$127.90	$127.90
Purchase #4	$216.77	12.548%	$243.9703	$243.97	$243.95	$244.00
Purchase #5	$121.92	11.641%	$136.1127	$136.11	$136.10	$136.10
Purchase #6	$10.77	12.246%	$12.0889	$12.09	$12.10	$12.10
Purchase #7	$90.68	9.639%	$99.4206	$99.42	$99.40	$99.40
7 purchase totals =	$816.41		$899.6140	$899.61	$899.55	$899.60