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	$218.46	3.773%	$226.7025	$226.70	$226.70	$226.70
Purchase #2	$128.72	11.784%	$143.8884	$143.89	$143.90	$143.90
Purchase #3	$221.60	4.413%	$231.3792	$231.38	$231.40	$231.40
Purchase #4	$78.67	11.249%	$87.5196	$87.52	$87.50	$87.50
Purchase #5	$118.97	11.442%	$132.5825	$132.58	$132.60	$132.60
Purchase #6	$196.68	11.259%	$218.8242	$218.82	$218.80	$218.80
Purchase #7	$160.72	13.588%	$182.5586	$182.56	$182.55	$182.60
7 purchase totals =	$1,123.82		$1,223.4550	$1,223.45	$1,223.45	$1,223.50