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	$130.67	8.498%	$141.7743	$141.77	$141.75	$141.80
Purchase #2	$41.30	6.181%	$43.8528	$43.85	$43.85	$43.90
Purchase #3	$84.61	11.510%	$94.3486	$94.35	$94.35	$94.30
Purchase #4	$109.44	3.855%	$113.6589	$113.66	$113.65	$113.70
Purchase #5	$197.74	5.447%	$208.5109	$208.51	$208.50	$208.50
Purchase #6	$77.47	4.178%	$80.7067	$80.71	$80.70	$80.70
Purchase #7	$94.53	6.431%	$100.6092	$100.61	$100.60	$100.60
7 purchase totals =	$735.76		$783.4614	$783.46	$783.40	$783.50