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	$133.72	5.839%	$141.5279	$141.53	$141.55	$141.50
Purchase #2	$240.59	5.144%	$252.9659	$252.97	$252.95	$253.00
Purchase #3	$75.59	6.856%	$80.7725	$80.77	$80.75	$80.80
Purchase #4	$116.37	7.123%	$124.659	$124.66	$124.65	$124.70
Purchase #5	$77.85	4.235%	$81.1469	$81.15	$81.15	$81.10
Purchase #6	$160.27	7.338%	$172.0306	$172.03	$172.05	$172.00
Purchase #7	$72.44	13.681%	$82.3505	$82.35	$82.35	$82.40
7 purchase totals =	$876.83		$935.4533	$935.46	$935.45	$935.50