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	$231.59	10.573%	$256.076	$256.08	$256.10	$256.10
Purchase #2	$75.39	7.250%	$80.8558	$80.86	$80.85	$80.90
Purchase #3	$49.81	11.677%	$55.6263	$55.63	$55.65	$55.60
Purchase #4	$175.28	6.374%	$186.4523	$186.45	$186.45	$186.50
Purchase #5	$182.54	8.874%	$198.7386	$198.74	$198.75	$198.70
Purchase #6	$182.97	11.740%	$204.4507	$204.45	$204.45	$204.50
Purchase #7	$207.61	5.295%	$218.6029	$218.60	$218.60	$218.60
7 purchase totals =	$1,105.19		$1,200.8026	$1,200.81	$1,200.85	$1,200.90