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	$233.45	12.445%	$262.5029	$262.50	$262.50	$262.50
Purchase #2	$217.46	6.652%	$231.9254	$231.93	$231.95	$231.90
Purchase #3	$136.76	7.185%	$146.5862	$146.59	$146.60	$146.60
Purchase #4	$43.73	6.384%	$46.5217	$46.52	$46.50	$46.50
Purchase #5	$195.46	12.307%	$219.5153	$219.52	$219.50	$219.50
Purchase #6	$153.42	6.176%	$162.8952	$162.90	$162.90	$162.90
Purchase #7	$228.31	12.665%	$257.2255	$257.23	$257.25	$257.20
7 purchase totals =	$1,208.59		$1,327.1722	$1,327.19	$1,327.20	$1,327.10