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	$58.26	7.330%	$62.5305	$62.53	$62.55	$62.50
Purchase #2	$93.71	6.850%	$100.1291	$100.13	$100.15	$100.10
Purchase #3	$161.25	4.277%	$168.1467	$168.15	$168.15	$168.10
Purchase #4	$147.93	7.536%	$159.078	$159.08	$159.10	$159.10
Purchase #5	$105.57	5.452%	$111.3257	$111.33	$111.35	$111.30
Purchase #6	$243.93	12.641%	$274.7652	$274.77	$274.75	$274.80
Purchase #7	$103.80	9.304%	$113.4576	$113.46	$113.45	$113.50
7 purchase totals =	$914.45		$989.4328	$989.45	$989.50	$989.40