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	$80.92	10.167%	$89.1471	$89.15	$89.15	$89.10
Purchase #2	$80.41	6.814%	$85.8891	$85.89	$85.90	$85.90
Purchase #3	$108.41	10.202%	$119.47	$119.47	$119.45	$119.50
Purchase #4	$34.32	6.255%	$36.4667	$36.47	$36.45	$36.50
Purchase #5	$20.25	13.253%	$22.9337	$22.93	$22.95	$22.90
Purchase #6	$41.50	8.583%	$45.0619	$45.06	$45.05	$45.10
Purchase #7	$40.42	13.704%	$45.9592	$45.96	$45.95	$46.00
7 purchase totals =	$406.23		$444.9277	$444.93	$444.90	$445.00