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	$168.66	9.225%	$184.2189	$184.22	$184.20	$184.20
Purchase #2	$123.75	10.365%	$136.5767	$136.58	$136.60	$136.60
Purchase #3	$20.50	5.340%	$21.5947	$21.59	$21.60	$21.60
Purchase #4	$208.46	5.464%	$219.8503	$219.85	$219.85	$219.90
Purchase #5	$182.37	3.406%	$188.5815	$188.58	$188.60	$188.60
Purchase #6	$180.52	5.720%	$190.8457	$190.85	$190.85	$190.80
Purchase #7	$188.37	6.608%	$200.8175	$200.82	$200.80	$200.80
7 purchase totals =	$1,072.63		$1,142.4853	$1,142.49	$1,142.50	$1,142.50