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	$126.52	12.388%	$142.1933	$142.19	$142.20	$142.20
Purchase #2	$183.77	5.386%	$193.6679	$193.67	$193.65	$193.70
Purchase #3	$42.85	4.770%	$44.8939	$44.89	$44.90	$44.90
Purchase #4	$156.52	6.354%	$166.4653	$166.47	$166.45	$166.50
Purchase #5	$68.68	3.217%	$70.8894	$70.89	$70.90	$70.90
Purchase #6	$105.71	10.161%	$116.4512	$116.45	$116.45	$116.50
Purchase #7	$177.50	7.253%	$190.3741	$190.37	$190.35	$190.40
7 purchase totals =	$861.55		$924.9351	$924.93	$924.90	$925.10