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	$152.98	7.497%	$164.4489	$164.45	$164.45	$164.40
Purchase #2	$155.31	13.700%	$176.5875	$176.59	$176.60	$176.60
Purchase #3	$164.92	12.612%	$185.7197	$185.72	$185.70	$185.70
Purchase #4	$89.51	6.643%	$95.4561	$95.46	$95.45	$95.50
Purchase #5	$11.86	11.407%	$13.2129	$13.21	$13.20	$13.20
Purchase #6	$230.82	10.691%	$255.497	$255.50	$255.50	$255.50
Purchase #7	$71.72	5.853%	$75.9178	$75.92	$75.90	$75.90
7 purchase totals =	$877.12		$966.8399	$966.85	$966.80	$966.80