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	$207.98	8.616%	$225.8996	$225.90	$225.90	$225.90
Purchase #2	$96.44	7.218%	$103.401	$103.40	$103.40	$103.40
Purchase #3	$108.82	3.354%	$112.4698	$112.47	$112.45	$112.50
Purchase #4	$227.94	13.154%	$257.9232	$257.92	$257.90	$257.90
Purchase #5	$162.52	5.727%	$171.8275	$171.83	$171.85	$171.80
Purchase #6	$235.67	8.825%	$256.4679	$256.47	$256.45	$256.50
Purchase #7	$48.27	12.647%	$54.3747	$54.37	$54.35	$54.40
7 purchase totals =	$1,087.64		$1,182.3637	$1,182.36	$1,182.30	$1,182.40