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	$247.86	4.781%	$259.7102	$259.71	$259.70	$259.70
Purchase #2	$210.80	9.798%	$231.4542	$231.45	$231.45	$231.50
Purchase #3	$64.27	7.383%	$69.0151	$69.02	$69.00	$69.00
Purchase #4	$155.82	3.151%	$160.7299	$160.73	$160.75	$160.70
Purchase #5	$29.42	10.618%	$32.5438	$32.54	$32.55	$32.50
Purchase #6	$144.97	3.835%	$150.5296	$150.53	$150.55	$150.50
Purchase #7	$111.77	11.461%	$124.58	$124.58	$124.60	$124.60
7 purchase totals =	$964.91		$1,028.5628	$1,028.56	$1,028.60	$1,028.50