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	$228.87	4.795%	$239.8443	$239.84	$239.85	$239.80
Purchase #2	$152.65	13.774%	$173.676	$173.68	$173.70	$173.70
Purchase #3	$31.74	3.646%	$32.8972	$32.90	$32.90	$32.90
Purchase #4	$134.29	6.804%	$143.4271	$143.43	$143.45	$143.40
Purchase #5	$199.99	13.866%	$227.7206	$227.72	$227.70	$227.70
Purchase #6	$35.70	4.830%	$37.4243	$37.42	$37.40	$37.40
Purchase #7	$132.29	13.805%	$150.5526	$150.55	$150.55	$150.60
7 purchase totals =	$915.53		$1,005.5421	$1,005.54	$1,005.55	$1,005.50