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	$22.31	13.649%	$25.3551	$25.36	$25.35	$25.40
Purchase #2	$50.45	7.337%	$54.1515	$54.15	$54.15	$54.20
Purchase #3	$61.62	13.328%	$69.8327	$69.83	$69.85	$69.80
Purchase #4	$220.84	4.759%	$231.3498	$231.35	$231.35	$231.30
Purchase #5	$86.67	6.325%	$92.1519	$92.15	$92.15	$92.20
Purchase #6	$151.25	8.475%	$164.0684	$164.07	$164.05	$164.10
Purchase #7	$82.54	3.601%	$85.5123	$85.51	$85.50	$85.50
7 purchase totals =	$675.68		$722.4217	$722.42	$722.40	$722.50