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	$77.53	11.401%	$86.3692	$86.37	$86.35	$86.40
Purchase #2	$190.65	8.529%	$206.9105	$206.91	$206.90	$206.90
Purchase #3	$188.92	9.227%	$206.3516	$206.35	$206.35	$206.40
Purchase #4	$63.53	4.713%	$66.5242	$66.52	$66.50	$66.50
Purchase #5	$52.39	13.185%	$59.2976	$59.30	$59.30	$59.30
Purchase #6	$74.60	10.138%	$82.1629	$82.16	$82.15	$82.20
Purchase #7	$21.79	9.553%	$23.8716	$23.87	$23.85	$23.90
7 purchase totals =	$669.41		$731.4876	$731.48	$731.40	$731.60