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	$117.98	6.426%	$125.5614	$125.56	$125.55	$125.60
Purchase #2	$134.51	13.806%	$153.0805	$153.08	$153.10	$153.10
Purchase #3	$71.37	13.555%	$81.0442	$81.04	$81.05	$81.00
Purchase #4	$57.52	12.195%	$64.5346	$64.53	$64.55	$64.50
Purchase #5	$85.79	9.835%	$94.2274	$94.23	$94.25	$94.20
Purchase #6	$167.64	6.838%	$179.1032	$179.10	$179.10	$179.10
Purchase #7	$78.75	13.348%	$89.2616	$89.26	$89.25	$89.30
7 purchase totals =	$713.56		$786.8129	$786.80	$786.85	$786.80