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	$33.77	7.118%	$36.1737	$36.17	$36.15	$36.20
Purchase #2	$153.36	3.384%	$158.5497	$158.55	$158.55	$158.50
Purchase #3	$55.55	3.676%	$57.592	$57.59	$57.60	$57.60
Purchase #4	$23.29	5.126%	$24.4838	$24.48	$24.50	$24.50
Purchase #5	$239.59	6.806%	$255.8965	$255.90	$255.90	$255.90
Purchase #6	$34.54	7.717%	$37.2055	$37.21	$37.20	$37.20
Purchase #7	$137.99	13.555%	$156.6945	$156.69	$156.70	$156.70
7 purchase totals =	$678.09		$726.5957	$726.59	$726.60	$726.60