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	$144.31	11.381%	$160.7339	$160.73	$160.75	$160.70
Purchase #2	$98.43	5.461%	$103.8053	$103.81	$103.80	$103.80
Purchase #3	$38.59	8.159%	$41.7386	$41.74	$41.75	$41.70
Purchase #4	$174.58	12.484%	$196.3746	$196.37	$196.35	$196.40
Purchase #5	$54.41	3.256%	$56.1816	$56.18	$56.20	$56.20
Purchase #6	$195.62	9.204%	$213.6249	$213.62	$213.60	$213.60
Purchase #7	$132.62	9.675%	$145.451	$145.45	$145.45	$145.50
7 purchase totals =	$838.56		$917.9099	$917.90	$917.90	$917.90