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	$78.42	10.354%	$86.5396	$86.54	$86.55	$86.50
Purchase #2	$10.35	3.848%	$10.7483	$10.75	$10.75	$10.70
Purchase #3	$184.67	13.597%	$209.7796	$209.78	$209.80	$209.80
Purchase #4	$103.75	7.270%	$111.2926	$111.29	$111.30	$111.30
Purchase #5	$98.32	7.262%	$105.46	$105.46	$105.45	$105.50
Purchase #6	$24.51	4.670%	$25.6546	$25.65	$25.65	$25.70
Purchase #7	$198.66	13.235%	$224.9527	$224.95	$224.95	$225.00
7 purchase totals =	$698.68		$774.4274	$774.42	$774.45	$774.50