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	$40.98	12.253%	$46.0013	$46.00	$46.00	$46.00
Purchase #2	$131.48	9.756%	$144.3072	$144.31	$144.30	$144.30
Purchase #3	$97.72	7.462%	$105.0119	$105.01	$105.00	$105.00
Purchase #4	$238.99	11.682%	$266.9088	$266.91	$266.90	$266.90
Purchase #5	$142.91	13.761%	$162.5758	$162.58	$162.60	$162.60
Purchase #6	$249.68	4.806%	$261.6796	$261.68	$261.70	$261.70
Purchase #7	$167.59	11.543%	$186.9349	$186.93	$186.95	$186.90
7 purchase totals =	$1,069.35		$1,173.4195	$1,173.42	$1,173.45	$1,173.40