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	$136.64	5.441%	$144.0746	$144.07	$144.05	$144.10
Purchase #2	$10.90	11.339%	$12.136	$12.14	$12.15	$12.10
Purchase #3	$123.76	6.657%	$131.9987	$132.00	$132.00	$132.00
Purchase #4	$10.94	10.486%	$12.0872	$12.09	$12.10	$12.10
Purchase #5	$198.45	13.208%	$224.6613	$224.66	$224.65	$224.70
Purchase #6	$232.28	12.639%	$261.6379	$261.64	$261.65	$261.60
Purchase #7	$186.69	5.373%	$196.7209	$196.72	$196.70	$196.70
7 purchase totals =	$899.66		$983.3166	$983.32	$983.30	$983.30