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	$50.29	4.817%	$52.7125	$52.71	$52.70	$52.70
Purchase #2	$66.98	6.252%	$71.1676	$71.17	$71.15	$71.20
Purchase #3	$81.74	5.178%	$85.9725	$85.97	$85.95	$86.00
Purchase #4	$34.37	10.439%	$37.9579	$37.96	$37.95	$38.00
Purchase #5	$94.82	9.256%	$103.5965	$103.60	$103.60	$103.60
Purchase #6	$212.68	8.615%	$231.0024	$231.00	$231.00	$231.00
Purchase #7	$117.67	11.658%	$131.388	$131.39	$131.40	$131.40
7 purchase totals =	$658.55		$713.7974	$713.80	$713.75	$713.90