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	$221.68	9.117%	$241.8906	$241.89	$241.90	$241.90
Purchase #2	$145.80	7.625%	$156.9173	$156.92	$156.90	$156.90
Purchase #3	$214.42	5.169%	$225.5034	$225.50	$225.50	$225.50
Purchase #4	$53.53	4.335%	$55.8505	$55.85	$55.85	$55.90
Purchase #5	$200.83	7.185%	$215.2596	$215.26	$215.25	$215.30
Purchase #6	$217.29	6.689%	$231.8245	$231.82	$231.80	$231.80
Purchase #7	$76.87	7.129%	$82.3501	$82.35	$82.35	$82.40
7 purchase totals =	$1,130.42		$1,209.5960	$1,209.59	$1,209.55	$1,209.70