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	$61.90	12.861%	$69.861	$69.86	$69.85	$69.90
Purchase #2	$146.58	13.595%	$166.5076	$166.51	$166.50	$166.50
Purchase #3	$40.25	9.703%	$44.1555	$44.16	$44.15	$44.20
Purchase #4	$78.87	4.403%	$82.3426	$82.34	$82.35	$82.30
Purchase #5	$187.73	6.141%	$199.2585	$199.26	$199.25	$199.30
Purchase #6	$92.36	3.356%	$95.4596	$95.46	$95.45	$95.50
Purchase #7	$47.31	3.438%	$48.9365	$48.94	$48.95	$48.90
7 purchase totals =	$655.00		$706.5213	$706.53	$706.50	$706.60