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	$121.72	8.215%	$131.7193	$131.72	$131.70	$131.70
Purchase #2	$135.81	12.205%	$152.3856	$152.39	$152.40	$152.40
Purchase #3	$212.51	13.545%	$241.2945	$241.29	$241.30	$241.30
Purchase #4	$71.79	8.487%	$77.8828	$77.88	$77.90	$77.90
Purchase #5	$38.84	7.677%	$41.8217	$41.82	$41.80	$41.80
Purchase #6	$233.47	11.595%	$260.5408	$260.54	$260.55	$260.50
Purchase #7	$156.54	6.288%	$166.3832	$166.38	$166.40	$166.40
7 purchase totals =	$970.68		$1,072.0279	$1,072.02	$1,072.05	$1,072.00