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	$161.51	4.382%	$168.5874	$168.59	$168.60	$168.60
Purchase #2	$51.52	11.695%	$57.5453	$57.55	$57.55	$57.50
Purchase #3	$56.49	7.308%	$60.6183	$60.62	$60.60	$60.60
Purchase #4	$176.54	13.793%	$200.8902	$200.89	$200.90	$200.90
Purchase #5	$31.99	4.496%	$33.4283	$33.43	$33.45	$33.40
Purchase #6	$114.86	7.542%	$123.5227	$123.52	$123.50	$123.50
Purchase #7	$83.37	4.658%	$87.2534	$87.25	$87.25	$87.30
7 purchase totals =	$676.28		$731.8456	$731.85	$731.85	$731.80