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	$119.59	3.156%	$123.3643	$123.36	$123.35	$123.40
Purchase #2	$36.39	3.376%	$37.6185	$37.62	$37.60	$37.60
Purchase #3	$206.46	3.872%	$214.4541	$214.45	$214.45	$214.50
Purchase #4	$33.89	13.280%	$38.3906	$38.39	$38.40	$38.40
Purchase #5	$34.87	7.783%	$37.5839	$37.58	$37.60	$37.60
Purchase #6	$60.57	9.450%	$66.2939	$66.29	$66.30	$66.30
Purchase #7	$124.76	12.760%	$140.6794	$140.68	$140.70	$140.70
7 purchase totals =	$616.53		$658.3847	$658.37	$658.40	$658.50