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	$66.82	13.390%	$75.7672	$75.77	$75.75	$75.80
Purchase #2	$208.48	3.354%	$215.4724	$215.47	$215.45	$215.50
Purchase #3	$108.64	13.332%	$123.1239	$123.12	$123.10	$123.10
Purchase #4	$65.28	13.146%	$73.8617	$73.86	$73.85	$73.90
Purchase #5	$208.25	6.837%	$222.4881	$222.49	$222.50	$222.50
Purchase #6	$81.55	9.871%	$89.5998	$89.60	$89.60	$89.60
Purchase #7	$239.68	9.108%	$261.5101	$261.51	$261.50	$261.50
7 purchase totals =	$978.70		$1,061.8232	$1,061.82	$1,061.75	$1,061.90