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	$57.60	5.667%	$60.8642	$60.86	$60.85	$60.90
Purchase #2	$143.89	4.812%	$150.814	$150.81	$150.80	$150.80
Purchase #3	$127.30	4.474%	$132.9954	$133.00	$133.00	$133.00
Purchase #4	$213.33	10.390%	$235.495	$235.50	$235.50	$235.50
Purchase #5	$210.86	7.380%	$226.4215	$226.42	$226.40	$226.40
Purchase #6	$107.61	3.493%	$111.3688	$111.37	$111.35	$111.40
Purchase #7	$229.91	3.267%	$237.4212	$237.42	$237.40	$237.40
7 purchase totals =	$1,090.50		$1,155.3801	$1,155.38	$1,155.30	$1,155.40