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	$231.78	4.354%	$241.8717	$241.87	$241.85	$241.90
Purchase #2	$52.90	8.572%	$57.4346	$57.43	$57.45	$57.40
Purchase #3	$202.26	5.443%	$213.269	$213.27	$213.25	$213.30
Purchase #4	$131.59	7.601%	$141.5922	$141.59	$141.60	$141.60
Purchase #5	$247.85	12.868%	$279.7433	$279.74	$279.75	$279.70
Purchase #6	$117.49	8.471%	$127.4426	$127.44	$127.45	$127.40
Purchase #7	$130.90	8.748%	$142.3511	$142.35	$142.35	$142.40
7 purchase totals =	$1,114.77		$1,203.7045	$1,203.69	$1,203.70	$1,203.70