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	$54.68	12.492%	$61.5106	$61.51	$61.50	$61.50
Purchase #2	$23.77	8.402%	$25.7672	$25.77	$25.75	$25.80
Purchase #3	$150.93	11.864%	$168.8363	$168.84	$168.85	$168.80
Purchase #4	$169.36	7.229%	$181.603	$181.60	$181.60	$181.60
Purchase #5	$25.47	10.831%	$28.2287	$28.23	$28.25	$28.20
Purchase #6	$152.95	5.286%	$161.0349	$161.03	$161.05	$161.00
Purchase #7	$141.90	3.314%	$146.6026	$146.60	$146.60	$146.60
7 purchase totals =	$719.06		$773.5833	$773.58	$773.60	$773.50