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	$67.53	5.686%	$71.3698	$71.37	$71.35	$71.40
Purchase #2	$134.87	12.733%	$152.043	$152.04	$152.05	$152.00
Purchase #3	$41.60	8.482%	$45.1285	$45.13	$45.15	$45.10
Purchase #4	$216.82	11.479%	$241.7088	$241.71	$241.70	$241.70
Purchase #5	$12.93	3.275%	$13.3535	$13.35	$13.35	$13.40
Purchase #6	$162.33	4.547%	$169.7111	$169.71	$169.70	$169.70
Purchase #7	$123.79	7.639%	$133.2463	$133.25	$133.25	$133.20
7 purchase totals =	$759.87		$826.5610	$826.56	$826.55	$826.50