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	$138.84	13.521%	$157.6126	$157.61	$157.60	$157.60
Purchase #2	$114.44	4.425%	$119.504	$119.50	$119.50	$119.50
Purchase #3	$122.93	3.663%	$127.4329	$127.43	$127.45	$127.40
Purchase #4	$196.52	4.737%	$205.8292	$205.83	$205.85	$205.80
Purchase #5	$161.97	5.655%	$171.1294	$171.13	$171.15	$171.10
Purchase #6	$238.45	4.638%	$249.5093	$249.51	$249.50	$249.50
Purchase #7	$137.78	3.592%	$142.7291	$142.73	$142.75	$142.70
7 purchase totals =	$1,110.93		$1,173.7465	$1,173.74	$1,173.80	$1,173.60