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	$62.65	6.672%	$66.83	$66.83	$66.85	$66.80
Purchase #2	$7.25	9.276%	$7.9225	$7.92	$7.90	$7.90
Purchase #3	$28.60	10.247%	$31.5306	$31.53	$31.55	$31.50
Purchase #4	$178.41	4.205%	$185.9121	$185.91	$185.90	$185.90
Purchase #5	$141.43	5.188%	$148.7674	$148.77	$148.75	$148.80
Purchase #6	$37.34	12.684%	$42.0762	$42.08	$42.10	$42.10
Purchase #7	$216.38	7.564%	$232.747	$232.75	$232.75	$232.70
7 purchase totals =	$672.06		$715.7858	$715.79	$715.80	$715.70