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	$247.96	4.668%	$259.5348	$259.53	$259.55	$259.50
Purchase #2	$92.31	7.847%	$99.5536	$99.55	$99.55	$99.60
Purchase #3	$182.26	12.481%	$205.0079	$205.01	$205.00	$205.00
Purchase #4	$112.30	3.697%	$116.4517	$116.45	$116.45	$116.50
Purchase #5	$209.87	13.860%	$238.958	$238.96	$238.95	$239.00
Purchase #6	$37.74	7.612%	$40.6128	$40.61	$40.60	$40.60
Purchase #7	$140.61	12.723%	$158.4998	$158.50	$158.50	$158.50
7 purchase totals =	$1,023.05		$1,118.6186	$1,118.61	$1,118.60	$1,118.70