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	$66.81	8.632%	$72.577	$72.58	$72.60	$72.60
Purchase #2	$41.47	11.583%	$46.2735	$46.27	$46.25	$46.30
Purchase #3	$99.71	4.153%	$103.851	$103.85	$103.85	$103.90
Purchase #4	$212.34	7.254%	$227.7431	$227.74	$227.75	$227.70
Purchase #5	$180.75	4.862%	$189.5381	$189.54	$189.55	$189.50
Purchase #6	$207.29	13.180%	$234.6108	$234.61	$234.60	$234.60
Purchase #7	$196.57	11.249%	$218.6822	$218.68	$218.70	$218.70
7 purchase totals =	$1,004.94		$1,093.2757	$1,093.27	$1,093.30	$1,093.30