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	$180.28	5.716%	$190.5848	$190.58	$190.60	$190.60
Purchase #2	$206.67	7.183%	$221.5151	$221.52	$221.50	$221.50
Purchase #3	$94.86	5.243%	$99.8335	$99.83	$99.85	$99.80
Purchase #4	$205.85	3.599%	$213.2585	$213.26	$213.25	$213.30
Purchase #5	$87.80	9.191%	$95.8697	$95.87	$95.85	$95.90
Purchase #6	$153.33	7.642%	$165.0475	$165.05	$165.05	$165.00
Purchase #7	$103.55	13.626%	$117.6597	$117.66	$117.65	$117.70
7 purchase totals =	$1,032.34		$1,103.7688	$1,103.77	$1,103.75	$1,103.80