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	$106.46	5.155%	$111.948	$111.95	$111.95	$111.90
Purchase #2	$48.94	6.448%	$52.0957	$52.10	$52.10	$52.10
Purchase #3	$27.90	6.309%	$29.6602	$29.66	$29.65	$29.70
Purchase #4	$135.77	10.854%	$150.5065	$150.51	$150.50	$150.50
Purchase #5	$247.49	13.451%	$280.7799	$280.78	$280.80	$280.80
Purchase #6	$135.60	13.183%	$153.4761	$153.48	$153.50	$153.50
Purchase #7	$218.45	9.420%	$239.028	$239.03	$239.05	$239.00
7 purchase totals =	$920.61		$1,017.4944	$1,017.51	$1,017.55	$1,017.50