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	$224.77	5.295%	$236.6716	$236.67	$236.65	$236.70
Purchase #2	$167.45	12.773%	$188.8384	$188.84	$188.85	$188.80
Purchase #3	$215.37	3.506%	$222.9209	$222.92	$222.90	$222.90
Purchase #4	$92.87	6.395%	$98.809	$98.81	$98.80	$98.80
Purchase #5	$52.36	4.696%	$54.8188	$54.82	$54.80	$54.80
Purchase #6	$57.87	13.273%	$65.5511	$65.55	$65.55	$65.60
Purchase #7	$82.25	5.182%	$86.5122	$86.51	$86.50	$86.50
7 purchase totals =	$892.94		$954.1220	$954.12	$954.05	$954.10