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	$51.48	6.127%	$54.6342	$54.63	$54.65	$54.60
Purchase #2	$139.71	10.242%	$154.0191	$154.02	$154.00	$154.00
Purchase #3	$146.28	7.448%	$157.1749	$157.17	$157.15	$157.20
Purchase #4	$226.55	3.601%	$234.7081	$234.71	$234.70	$234.70
Purchase #5	$89.60	11.440%	$99.8502	$99.85	$99.85	$99.90
Purchase #6	$241.59	7.576%	$259.8929	$259.89	$259.90	$259.90
Purchase #7	$46.44	13.725%	$52.8139	$52.81	$52.80	$52.80
7 purchase totals =	$941.65		$1,013.0933	$1,013.08	$1,013.05	$1,013.10