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	$95.31	10.832%	$105.634	$105.63	$105.65	$105.60
Purchase #2	$151.47	5.311%	$159.5146	$159.51	$159.50	$159.50
Purchase #3	$64.39	12.493%	$72.4342	$72.43	$72.45	$72.40
Purchase #4	$247.57	13.118%	$280.0462	$280.05	$280.05	$280.00
Purchase #5	$142.60	8.733%	$155.0533	$155.05	$155.05	$155.10
Purchase #6	$229.81	6.369%	$244.4466	$244.45	$244.45	$244.40
Purchase #7	$169.70	7.378%	$182.2205	$182.22	$182.20	$182.20
7 purchase totals =	$1,100.85		$1,199.3494	$1,199.34	$1,199.35	$1,199.20