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	$62.46	13.689%	$71.0101	$71.01	$71.00	$71.00
Purchase #2	$206.61	7.577%	$222.2648	$222.26	$222.25	$222.30
Purchase #3	$125.27	7.235%	$134.3333	$134.33	$134.35	$134.30
Purchase #4	$25.97	12.373%	$29.1833	$29.18	$29.20	$29.20
Purchase #5	$107.68	3.429%	$111.3723	$111.37	$111.35	$111.40
Purchase #6	$55.58	4.240%	$57.9366	$57.94	$57.95	$57.90
Purchase #7	$74.47	5.282%	$78.4035	$78.40	$78.40	$78.40
7 purchase totals =	$658.04		$704.5039	$704.49	$704.50	$704.50