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	$247.82	7.225%	$265.725	$265.73	$265.75	$265.70
Purchase #2	$38.39	13.557%	$43.5945	$43.59	$43.60	$43.60
Purchase #3	$138.49	4.707%	$145.0087	$145.01	$145.00	$145.00
Purchase #4	$138.85	4.335%	$144.8691	$144.87	$144.85	$144.90
Purchase #5	$171.75	7.456%	$184.5557	$184.56	$184.55	$184.60
Purchase #6	$102.73	12.269%	$115.3339	$115.33	$115.35	$115.30
Purchase #7	$38.46	4.689%	$40.2634	$40.26	$40.25	$40.30
7 purchase totals =	$876.49		$939.3503	$939.35	$939.35	$939.40