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	$233.61	13.194%	$264.4325	$264.43	$264.45	$264.40
Purchase #2	$132.37	4.417%	$138.2168	$138.22	$138.20	$138.20
Purchase #3	$70.80	3.833%	$73.5138	$73.51	$73.50	$73.50
Purchase #4	$95.94	9.538%	$105.0908	$105.09	$105.10	$105.10
Purchase #5	$67.30	7.179%	$72.1315	$72.13	$72.15	$72.10
Purchase #6	$76.76	11.238%	$85.3863	$85.39	$85.40	$85.40
Purchase #7	$153.35	6.471%	$163.2733	$163.27	$163.25	$163.30
7 purchase totals =	$830.13		$902.0450	$902.04	$902.05	$902.00