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	$227.59	8.266%	$246.4026	$246.40	$246.40	$246.40
Purchase #2	$208.55	9.589%	$228.5479	$228.55	$228.55	$228.50
Purchase #3	$89.97	10.278%	$99.2171	$99.22	$99.20	$99.20
Purchase #4	$215.86	5.559%	$227.8597	$227.86	$227.85	$227.90
Purchase #5	$132.42	12.372%	$148.803	$148.80	$148.80	$148.80
Purchase #6	$108.81	9.227%	$118.8499	$118.85	$118.85	$118.80
Purchase #7	$29.41	11.241%	$32.716	$32.72	$32.70	$32.70
7 purchase totals =	$1,012.61		$1,102.3962	$1,102.40	$1,102.35	$1,102.30