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	$118.71	3.698%	$123.0999	$123.10	$123.10	$123.10
Purchase #2	$221.91	7.533%	$238.6265	$238.63	$238.65	$238.60
Purchase #3	$101.47	10.858%	$112.4876	$112.49	$112.50	$112.50
Purchase #4	$134.35	9.108%	$146.5866	$146.59	$146.60	$146.60
Purchase #5	$44.86	3.248%	$46.3171	$46.32	$46.30	$46.30
Purchase #6	$44.89	7.853%	$48.4152	$48.42	$48.40	$48.40
Purchase #7	$36.45	12.768%	$41.1039	$41.10	$41.10	$41.10
7 purchase totals =	$702.64		$756.6368	$756.65	$756.65	$756.60