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	$227.72	9.146%	$248.5473	$248.55	$248.55	$248.50
Purchase #2	$167.67	3.177%	$172.9969	$173.00	$173.00	$173.00
Purchase #3	$69.32	13.447%	$78.6415	$78.64	$78.65	$78.60
Purchase #4	$200.41	6.318%	$213.0719	$213.07	$213.05	$213.10
Purchase #5	$31.84	6.437%	$33.8895	$33.89	$33.90	$33.90
Purchase #6	$48.25	13.864%	$54.9394	$54.94	$54.95	$54.90
Purchase #7	$95.32	4.176%	$99.3006	$99.30	$99.30	$99.30
7 purchase totals =	$840.53		$901.3871	$901.39	$901.40	$901.30