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	$82.81	11.604%	$92.4193	$92.42	$92.40	$92.40
Purchase #2	$120.90	5.783%	$127.8916	$127.89	$127.90	$127.90
Purchase #3	$206.25	10.676%	$228.2693	$228.27	$228.25	$228.30
Purchase #4	$165.60	9.196%	$180.8286	$180.83	$180.85	$180.80
Purchase #5	$38.73	10.744%	$42.8912	$42.89	$42.90	$42.90
Purchase #6	$238.51	5.777%	$252.2887	$252.29	$252.30	$252.30
Purchase #7	$121.26	5.556%	$127.9972	$128.00	$128.00	$128.00
7 purchase totals =	$974.06		$1,052.5859	$1,052.59	$1,052.60	$1,052.60