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	$72.25	12.867%	$81.5464	$81.55	$81.55	$81.50
Purchase #2	$94.88	11.346%	$105.6451	$105.65	$105.65	$105.60
Purchase #3	$100.76	10.388%	$111.2269	$111.23	$111.25	$111.20
Purchase #4	$229.93	3.402%	$237.7522	$237.75	$237.75	$237.80
Purchase #5	$155.55	11.314%	$173.1489	$173.15	$173.15	$173.10
Purchase #6	$218.55	8.146%	$236.3531	$236.35	$236.35	$236.40
Purchase #7	$150.95	8.535%	$163.8336	$163.83	$163.85	$163.80
7 purchase totals =	$1,022.87		$1,109.5062	$1,109.51	$1,109.55	$1,109.40