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	$96.90	13.111%	$109.6046	$109.60	$109.60	$109.60
Purchase #2	$37.71	4.840%	$39.5352	$39.54	$39.55	$39.50
Purchase #3	$94.69	11.842%	$105.9032	$105.90	$105.90	$105.90
Purchase #4	$11.44	4.494%	$11.9541	$11.95	$11.95	$12.00
Purchase #5	$112.89	5.103%	$118.6508	$118.65	$118.65	$118.70
Purchase #6	$141.29	3.205%	$145.8183	$145.82	$145.80	$145.80
Purchase #7	$236.90	9.189%	$258.6687	$258.67	$258.65	$258.70
7 purchase totals =	$731.82		$790.1349	$790.13	$790.10	$790.20