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	$109.39	6.831%	$116.8624	$116.86	$116.85	$116.90
Purchase #2	$118.96	6.340%	$126.5021	$126.50	$126.50	$126.50
Purchase #3	$73.89	10.317%	$81.5132	$81.51	$81.50	$81.50
Purchase #4	$70.94	13.169%	$80.2821	$80.28	$80.30	$80.30
Purchase #5	$217.92	11.700%	$243.4166	$243.42	$243.40	$243.40
Purchase #6	$141.74	3.282%	$146.3919	$146.39	$146.40	$146.40
Purchase #7	$168.25	7.488%	$180.8486	$180.85	$180.85	$180.80
7 purchase totals =	$901.09		$975.8169	$975.81	$975.80	$975.80