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	$241.66	6.327%	$256.9498	$256.95	$256.95	$256.90
Purchase #2	$192.90	9.172%	$210.5928	$210.59	$210.60	$210.60
Purchase #3	$164.34	10.320%	$181.2999	$181.30	$181.30	$181.30
Purchase #4	$127.56	10.653%	$141.149	$141.15	$141.15	$141.10
Purchase #5	$132.84	9.368%	$145.2845	$145.28	$145.30	$145.30
Purchase #6	$123.60	5.625%	$130.5525	$130.55	$130.55	$130.60
Purchase #7	$63.76	5.689%	$67.3873	$67.39	$67.40	$67.40
7 purchase totals =	$1,046.66		$1,133.2158	$1,133.21	$1,133.25	$1,133.20