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	$241.65	11.262%	$268.8646	$268.86	$268.85	$268.90
Purchase #2	$153.34	13.777%	$174.4657	$174.47	$174.45	$174.50
Purchase #3	$28.89	9.650%	$31.6779	$31.68	$31.70	$31.70
Purchase #4	$237.34	11.829%	$265.4149	$265.41	$265.40	$265.40
Purchase #5	$234.68	6.602%	$250.1736	$250.17	$250.15	$250.20
Purchase #6	$100.67	3.175%	$103.8663	$103.87	$103.85	$103.90
Purchase #7	$100.85	3.580%	$104.4604	$104.46	$104.45	$104.50
7 purchase totals =	$1,097.42		$1,198.9234	$1,198.92	$1,198.85	$1,199.10