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	$207.99	8.326%	$225.3072	$225.31	$225.30	$225.30
Purchase #2	$150.37	3.851%	$156.1607	$156.16	$156.15	$156.20
Purchase #3	$105.97	11.257%	$117.899	$117.90	$117.90	$117.90
Purchase #4	$158.85	10.498%	$175.5261	$175.53	$175.55	$175.50
Purchase #5	$89.76	12.410%	$100.8992	$100.90	$100.90	$100.90
Purchase #6	$187.47	9.147%	$204.6179	$204.62	$204.60	$204.60
Purchase #7	$86.86	4.703%	$90.945	$90.95	$90.95	$90.90
7 purchase totals =	$987.27		$1,071.3551	$1,071.37	$1,071.35	$1,071.30