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	$148.45	5.755%	$156.9933	$156.99	$157.00	$157.00
Purchase #2	$65.52	10.615%	$72.4749	$72.47	$72.45	$72.50
Purchase #3	$31.26	7.360%	$33.5607	$33.56	$33.55	$33.60
Purchase #4	$54.39	13.835%	$61.9149	$61.91	$61.90	$61.90
Purchase #5	$63.71	4.827%	$66.7853	$66.79	$66.80	$66.80
Purchase #6	$6.57	11.735%	$7.341	$7.34	$7.35	$7.30
Purchase #7	$72.81	6.576%	$77.598	$77.60	$77.60	$77.60
7 purchase totals =	$442.71		$476.6681	$476.66	$476.65	$476.70