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	$34.99	7.490%	$37.6108	$37.61	$37.60	$37.60
Purchase #2	$45.27	5.702%	$47.8513	$47.85	$47.85	$47.90
Purchase #3	$162.40	6.828%	$173.4887	$173.49	$173.50	$173.50
Purchase #4	$159.31	10.397%	$175.8735	$175.87	$175.85	$175.90
Purchase #5	$40.34	4.791%	$42.2727	$42.27	$42.25	$42.30
Purchase #6	$83.68	4.594%	$87.5243	$87.52	$87.50	$87.50
Purchase #7	$219.31	3.107%	$226.124	$226.12	$226.10	$226.10
7 purchase totals =	$745.30		$790.7453	$790.73	$790.65	$790.80