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	$171.47	9.686%	$188.0786	$188.08	$188.10	$188.10
Purchase #2	$213.48	3.725%	$221.4321	$221.43	$221.45	$221.40
Purchase #3	$81.51	7.540%	$87.6559	$87.66	$87.65	$87.70
Purchase #4	$210.32	6.243%	$223.4503	$223.45	$223.45	$223.50
Purchase #5	$210.94	7.772%	$227.3343	$227.33	$227.35	$227.30
Purchase #6	$191.68	9.646%	$210.1695	$210.17	$210.15	$210.20
Purchase #7	$20.43	4.689%	$21.388	$21.39	$21.40	$21.40
7 purchase totals =	$1,099.83		$1,179.5087	$1,179.51	$1,179.55	$1,179.60