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	$48.45	6.564%	$51.6303	$51.63	$51.65	$51.60
Purchase #2	$109.85	10.610%	$121.5051	$121.51	$121.50	$121.50
Purchase #3	$90.43	6.854%	$96.6281	$96.63	$96.65	$96.60
Purchase #4	$83.46	3.366%	$86.2693	$86.27	$86.25	$86.30
Purchase #5	$83.49	10.808%	$92.5136	$92.51	$92.50	$92.50
Purchase #6	$55.39	11.597%	$61.8136	$61.81	$61.80	$61.80
Purchase #7	$179.83	7.239%	$192.8479	$192.85	$192.85	$192.80
7 purchase totals =	$650.90		$703.2079	$703.21	$703.20	$703.10