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	$9.48	13.108%	$10.7226	$10.72	$10.70	$10.70
Purchase #2	$100.54	3.377%	$103.9352	$103.94	$103.95	$103.90
Purchase #3	$117.75	13.298%	$133.4084	$133.41	$133.40	$133.40
Purchase #4	$167.83	8.373%	$181.8824	$181.88	$181.90	$181.90
Purchase #5	$146.68	9.682%	$160.8816	$160.88	$160.90	$160.90
Purchase #6	$147.51	3.449%	$152.5976	$152.60	$152.60	$152.60
Purchase #7	$167.60	3.210%	$172.98	$172.98	$173.00	$173.00
7 purchase totals =	$857.39		$916.4078	$916.41	$916.45	$916.40