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	$209.43	13.448%	$237.5941	$237.59	$237.60	$237.60
Purchase #2	$229.85	11.147%	$255.4714	$255.47	$255.45	$255.50
Purchase #3	$85.48	11.392%	$95.2179	$95.22	$95.20	$95.20
Purchase #4	$48.69	10.631%	$53.8662	$53.87	$53.85	$53.90
Purchase #5	$126.85	10.785%	$140.5308	$140.53	$140.55	$140.50
Purchase #6	$144.44	9.786%	$158.5749	$158.57	$158.55	$158.60
Purchase #7	$86.52	10.128%	$95.2827	$95.28	$95.30	$95.30
7 purchase totals =	$931.26		$1,036.5380	$1,036.53	$1,036.50	$1,036.60