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	$219.30	4.828%	$229.8878	$229.89	$229.90	$229.90
Purchase #2	$18.48	4.511%	$19.3136	$19.31	$19.30	$19.30
Purchase #3	$204.45	6.535%	$217.8108	$217.81	$217.80	$217.80
Purchase #4	$103.25	4.209%	$107.5958	$107.60	$107.60	$107.60
Purchase #5	$172.78	6.840%	$184.5982	$184.60	$184.60	$184.60
Purchase #6	$78.25	3.163%	$80.725	$80.73	$80.75	$80.70
Purchase #7	$39.32	3.554%	$40.7174	$40.72	$40.70	$40.70
7 purchase totals =	$835.83		$880.6486	$880.66	$880.65	$880.60