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	$53.46	13.323%	$60.5825	$60.58	$60.60	$60.60
Purchase #2	$93.60	6.286%	$99.4837	$99.48	$99.50	$99.50
Purchase #3	$62.94	5.767%	$66.5697	$66.57	$66.55	$66.60
Purchase #4	$36.30	3.182%	$37.4551	$37.46	$37.45	$37.50
Purchase #5	$27.97	11.282%	$31.1256	$31.13	$31.15	$31.10
Purchase #6	$18.50	5.868%	$19.5856	$19.59	$19.60	$19.60
Purchase #7	$76.68	13.127%	$86.7458	$86.75	$86.75	$86.70
7 purchase totals =	$369.45		$401.5480	$401.56	$401.60	$401.60