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	$114.60	3.142%	$118.2007	$118.20	$118.20	$118.20
Purchase #2	$69.35	13.713%	$78.86	$78.86	$78.85	$78.90
Purchase #3	$59.33	12.176%	$66.554	$66.55	$66.55	$66.60
Purchase #4	$163.35	11.598%	$182.2953	$182.30	$182.30	$182.30
Purchase #5	$25.76	13.170%	$29.1526	$29.15	$29.15	$29.20
Purchase #6	$36.36	5.559%	$38.3813	$38.38	$38.40	$38.40
Purchase #7	$40.71	3.429%	$42.1059	$42.11	$42.10	$42.10
7 purchase totals =	$509.46		$555.5498	$555.55	$555.55	$555.70