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	$32.25	3.731%	$33.4532	$33.45	$33.45	$33.50
Purchase #2	$88.98	7.789%	$95.9107	$95.91	$95.90	$95.90
Purchase #3	$94.57	6.615%	$100.8258	$100.83	$100.85	$100.80
Purchase #4	$247.35	13.166%	$279.9161	$279.92	$279.90	$279.90
Purchase #5	$177.60	5.512%	$187.3893	$187.39	$187.40	$187.40
Purchase #6	$55.95	11.127%	$62.1756	$62.18	$62.20	$62.20
Purchase #7	$24.93	10.681%	$27.5928	$27.59	$27.60	$27.60
7 purchase totals =	$721.63		$787.2635	$787.27	$787.30	$787.30