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	$54.96	4.520%	$57.4442	$57.44	$57.45	$57.40
Purchase #2	$126.52	13.872%	$144.0709	$144.07	$144.05	$144.10
Purchase #3	$95.77	10.305%	$105.6391	$105.64	$105.65	$105.60
Purchase #4	$146.58	11.177%	$162.9632	$162.96	$162.95	$163.00
Purchase #5	$199.25	8.585%	$216.3556	$216.36	$216.35	$216.40
Purchase #6	$213.40	10.462%	$235.7259	$235.73	$235.75	$235.70
Purchase #7	$186.90	5.159%	$196.5422	$196.54	$196.55	$196.50
7 purchase totals =	$1,023.38		$1,118.7411	$1,118.74	$1,118.75	$1,118.70