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	$141.40	9.391%	$154.6789	$154.68	$154.70	$154.70
Purchase #2	$246.54	11.271%	$274.3275	$274.33	$274.35	$274.30
Purchase #3	$89.78	11.233%	$99.865	$99.87	$99.85	$99.90
Purchase #4	$233.85	12.265%	$262.5317	$262.53	$262.55	$262.50
Purchase #5	$236.99	7.393%	$254.5107	$254.51	$254.50	$254.50
Purchase #6	$164.64	4.833%	$172.5971	$172.60	$172.60	$172.60
Purchase #7	$137.96	5.708%	$145.8348	$145.83	$145.85	$145.80
7 purchase totals =	$1,251.16		$1,364.3457	$1,364.35	$1,364.40	$1,364.30