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	$55.27	10.691%	$61.1789	$61.18	$61.20	$61.20
Purchase #2	$81.97	10.487%	$90.5662	$90.57	$90.55	$90.60
Purchase #3	$56.43	5.505%	$59.5365	$59.54	$59.55	$59.50
Purchase #4	$72.66	12.389%	$81.6618	$81.66	$81.65	$81.70
Purchase #5	$178.87	7.801%	$192.8236	$192.82	$192.80	$192.80
Purchase #6	$157.75	4.366%	$164.6374	$164.64	$164.65	$164.60
Purchase #7	$81.77	5.637%	$86.3794	$86.38	$86.40	$86.40
7 purchase totals =	$684.72		$736.7838	$736.79	$736.80	$736.80