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	$11.69	4.244%	$12.1861	$12.19	$12.20	$12.20
Purchase #2	$57.33	4.572%	$59.9511	$59.95	$59.95	$60.00
Purchase #3	$197.72	12.810%	$223.0479	$223.05	$223.05	$223.00
Purchase #4	$169.35	4.831%	$177.5313	$177.53	$177.55	$177.50
Purchase #5	$238.55	7.294%	$255.9498	$255.95	$255.95	$255.90
Purchase #6	$118.81	11.329%	$132.27	$132.27	$132.25	$132.30
Purchase #7	$148.90	5.480%	$157.0597	$157.06	$157.05	$157.10
7 purchase totals =	$942.35		$1,017.9959	$1,018.00	$1,018.00	$1,018.00