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	$136.64	5.322%	$143.912	$143.91	$143.90	$143.90
Purchase #2	$29.98	9.866%	$32.9378	$32.94	$32.95	$32.90
Purchase #3	$24.99	12.638%	$28.1482	$28.15	$28.15	$28.10
Purchase #4	$138.65	3.267%	$143.1797	$143.18	$143.20	$143.20
Purchase #5	$94.61	11.161%	$105.1694	$105.17	$105.15	$105.20
Purchase #6	$36.52	4.326%	$38.0999	$38.10	$38.10	$38.10
Purchase #7	$207.56	6.530%	$221.1137	$221.11	$221.10	$221.10
7 purchase totals =	$668.95		$712.5607	$712.56	$712.55	$712.50