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	$161.96	6.132%	$171.8914	$171.89	$171.90	$171.90
Purchase #2	$169.34	6.680%	$180.6519	$180.65	$180.65	$180.70
Purchase #3	$148.82	4.770%	$155.9187	$155.92	$155.90	$155.90
Purchase #4	$113.86	12.847%	$128.4876	$128.49	$128.50	$128.50
Purchase #5	$13.70	7.463%	$14.7224	$14.72	$14.70	$14.70
Purchase #6	$135.66	6.573%	$144.5769	$144.58	$144.60	$144.60
Purchase #7	$164.98	11.639%	$184.182	$184.18	$184.20	$184.20
7 purchase totals =	$908.32		$980.4309	$980.43	$980.45	$980.50