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	$42.48	8.768%	$46.2046	$46.20	$46.20	$46.20
Purchase #2	$133.52	11.549%	$148.9402	$148.94	$148.95	$148.90
Purchase #3	$13.68	5.165%	$14.3866	$14.39	$14.40	$14.40
Purchase #4	$52.71	6.566%	$56.1709	$56.17	$56.15	$56.20
Purchase #5	$39.60	7.207%	$42.454	$42.45	$42.45	$42.50
Purchase #6	$92.93	7.832%	$100.2083	$100.21	$100.20	$100.20
Purchase #7	$148.79	10.870%	$164.9635	$164.96	$164.95	$165.00
7 purchase totals =	$523.71		$573.3281	$573.32	$573.30	$573.40