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	$242.60	10.602%	$268.3205	$268.32	$268.30	$268.30
Purchase #2	$210.85	6.271%	$224.0724	$224.07	$224.05	$224.10
Purchase #3	$155.95	7.485%	$167.6229	$167.62	$167.60	$167.60
Purchase #4	$99.35	3.158%	$102.4875	$102.49	$102.50	$102.50
Purchase #5	$88.65	7.379%	$95.1915	$95.19	$95.20	$95.20
Purchase #6	$159.54	12.250%	$179.0837	$179.08	$179.10	$179.10
Purchase #7	$174.83	12.402%	$196.5124	$196.51	$196.50	$196.50
7 purchase totals =	$1,131.77		$1,233.2909	$1,233.28	$1,233.25	$1,233.30