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	$152.52	10.530%	$168.5804	$168.58	$168.60	$168.60
Purchase #2	$240.60	9.496%	$263.4474	$263.45	$263.45	$263.40
Purchase #3	$173.59	9.564%	$190.1921	$190.19	$190.20	$190.20
Purchase #4	$28.30	4.576%	$29.595	$29.60	$29.60	$29.60
Purchase #5	$200.59	5.502%	$211.6265	$211.63	$211.65	$211.60
Purchase #6	$38.38	12.131%	$43.0359	$43.04	$43.05	$43.00
Purchase #7	$51.84	9.276%	$56.6487	$56.65	$56.65	$56.60
7 purchase totals =	$885.82		$963.1260	$963.14	$963.20	$963.00