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	$207.67	13.652%	$236.0211	$236.02	$236.00	$236.00
Purchase #2	$83.36	7.323%	$89.4645	$89.46	$89.45	$89.50
Purchase #3	$18.58	11.231%	$20.6667	$20.67	$20.65	$20.70
Purchase #4	$93.68	7.734%	$100.9252	$100.93	$100.95	$100.90
Purchase #5	$127.35	5.499%	$134.353	$134.35	$134.35	$134.40
Purchase #6	$64.79	10.473%	$71.5755	$71.58	$71.60	$71.60
Purchase #7	$138.68	3.549%	$143.6018	$143.60	$143.60	$143.60
7 purchase totals =	$734.11		$796.6078	$796.61	$796.60	$796.70