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	$119.41	5.691%	$126.2056	$126.21	$126.20	$126.20
Purchase #2	$133.47	4.193%	$139.0664	$139.07	$139.05	$139.10
Purchase #3	$56.47	13.415%	$64.0455	$64.05	$64.05	$64.00
Purchase #4	$182.75	7.689%	$196.8016	$196.80	$196.80	$196.80
Purchase #5	$130.48	5.351%	$137.462	$137.46	$137.45	$137.50
Purchase #6	$180.72	10.827%	$200.2866	$200.29	$200.30	$200.30
Purchase #7	$202.76	6.826%	$216.6004	$216.60	$216.60	$216.60
7 purchase totals =	$1,006.06		$1,080.4681	$1,080.48	$1,080.45	$1,080.50