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	$103.60	10.498%	$114.4759	$114.48	$114.50	$114.50
Purchase #2	$180.89	13.513%	$205.3337	$205.33	$205.35	$205.30
Purchase #3	$40.78	7.690%	$43.916	$43.92	$43.90	$43.90
Purchase #4	$21.49	6.274%	$22.8383	$22.84	$22.85	$22.80
Purchase #5	$42.28	3.530%	$43.7725	$43.77	$43.75	$43.80
Purchase #6	$231.77	3.311%	$239.4439	$239.44	$239.45	$239.40
Purchase #7	$88.52	8.233%	$95.8079	$95.81	$95.80	$95.80
7 purchase totals =	$709.33		$765.5882	$765.59	$765.60	$765.50