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	$150.59	5.465%	$158.8197	$158.82	$158.80	$158.80
Purchase #2	$190.50	13.350%	$215.9318	$215.93	$215.95	$215.90
Purchase #3	$104.27	8.516%	$113.1496	$113.15	$113.15	$113.10
Purchase #4	$38.82	12.331%	$43.6069	$43.61	$43.60	$43.60
Purchase #5	$74.72	7.708%	$80.4794	$80.48	$80.50	$80.50
Purchase #6	$90.70	4.421%	$94.7098	$94.71	$94.70	$94.70
Purchase #7	$12.33	3.351%	$12.7432	$12.74	$12.75	$12.70
7 purchase totals =	$661.93		$719.4404	$719.44	$719.45	$719.30