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	$247.80	4.183%	$258.1655	$258.17	$258.15	$258.20
Purchase #2	$239.86	7.337%	$257.4585	$257.46	$257.45	$257.50
Purchase #3	$75.46	6.614%	$80.4509	$80.45	$80.45	$80.50
Purchase #4	$85.60	10.259%	$94.3817	$94.38	$94.40	$94.40
Purchase #5	$5.86	9.439%	$6.4131	$6.41	$6.40	$6.40
Purchase #6	$173.32	13.521%	$196.7546	$196.75	$196.75	$196.80
Purchase #7	$103.90	3.783%	$107.8305	$107.83	$107.85	$107.80
7 purchase totals =	$931.80		$1,001.4548	$1,001.45	$1,001.45	$1,001.60