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	$152.40	9.228%	$166.4635	$166.46	$166.45	$166.50
Purchase #2	$131.31	5.872%	$139.0205	$139.02	$139.00	$139.00
Purchase #3	$180.89	7.484%	$194.4278	$194.43	$194.45	$194.40
Purchase #4	$112.61	4.227%	$117.37	$117.37	$117.35	$117.40
Purchase #5	$72.28	10.520%	$79.8839	$79.88	$79.90	$79.90
Purchase #6	$143.55	10.444%	$158.5424	$158.54	$158.55	$158.50
Purchase #7	$19.74	8.871%	$21.4911	$21.49	$21.50	$21.50
7 purchase totals =	$812.78		$877.1992	$877.19	$877.20	$877.20