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	$211.50	6.124%	$224.4523	$224.45	$224.45	$224.50
Purchase #2	$158.37	5.564%	$167.1817	$167.18	$167.20	$167.20
Purchase #3	$136.48	11.505%	$152.182	$152.18	$152.20	$152.20
Purchase #4	$239.26	6.765%	$255.4459	$255.45	$255.45	$255.40
Purchase #5	$66.59	5.752%	$70.4203	$70.42	$70.40	$70.40
Purchase #6	$183.96	11.414%	$204.9572	$204.96	$204.95	$205.00
Purchase #7	$184.40	6.756%	$196.8581	$196.86	$196.85	$196.90
7 purchase totals =	$1,180.56		$1,271.4975	$1,271.50	$1,271.50	$1,271.60