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	$143.87	3.370%	$148.7184	$148.72	$148.70	$148.70
Purchase #2	$45.51	10.346%	$50.2185	$50.22	$50.20	$50.20
Purchase #3	$70.31	7.692%	$75.7182	$75.72	$75.70	$75.70
Purchase #4	$184.58	6.314%	$196.2344	$196.23	$196.25	$196.20
Purchase #5	$137.32	3.596%	$142.258	$142.26	$142.25	$142.30
Purchase #6	$127.82	10.610%	$141.3817	$141.38	$141.40	$141.40
Purchase #7	$179.74	9.342%	$196.5313	$196.53	$196.55	$196.50
7 purchase totals =	$889.15		$951.0605	$951.06	$951.05	$951.00