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	$112.62	13.281%	$127.5771	$127.58	$127.60	$127.60
Purchase #2	$68.80	5.756%	$72.7601	$72.76	$72.75	$72.80
Purchase #3	$131.37	9.693%	$144.1037	$144.10	$144.10	$144.10
Purchase #4	$113.29	13.801%	$128.9252	$128.93	$128.95	$128.90
Purchase #5	$131.82	8.416%	$142.914	$142.91	$142.90	$142.90
Purchase #6	$137.75	10.712%	$152.5058	$152.51	$152.50	$152.50
Purchase #7	$217.68	6.564%	$231.9685	$231.97	$231.95	$232.00
7 purchase totals =	$913.33		$1,000.7544	$1,000.76	$1,000.75	$1,000.80