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	$107.35	5.297%	$113.0363	$113.04	$113.05	$113.00
Purchase #2	$247.25	13.435%	$280.468	$280.47	$280.45	$280.50
Purchase #3	$71.72	9.386%	$78.4516	$78.45	$78.45	$78.50
Purchase #4	$111.30	11.864%	$124.5046	$124.50	$124.50	$124.50
Purchase #5	$125.42	4.248%	$130.7478	$130.75	$130.75	$130.70
Purchase #6	$40.66	8.379%	$44.0669	$44.07	$44.05	$44.10
Purchase #7	$241.51	6.343%	$256.829	$256.83	$256.85	$256.80
7 purchase totals =	$945.21		$1,028.1042	$1,028.11	$1,028.10	$1,028.10