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	$53.94	10.457%	$59.5805	$59.58	$59.60	$59.60
Purchase #2	$58.37	8.446%	$63.2999	$63.30	$63.30	$63.30
Purchase #3	$211.47	12.352%	$237.5908	$237.59	$237.60	$237.60
Purchase #4	$96.80	8.700%	$105.2216	$105.22	$105.20	$105.20
Purchase #5	$108.82	9.605%	$119.2722	$119.27	$119.25	$119.30
Purchase #6	$220.31	10.762%	$244.0198	$244.02	$244.00	$244.00
Purchase #7	$137.67	11.332%	$153.2708	$153.27	$153.25	$153.30
7 purchase totals =	$887.38		$982.2556	$982.25	$982.20	$982.30