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	$136.75	3.441%	$141.4556	$141.46	$141.45	$141.50
Purchase #2	$217.69	5.693%	$230.0831	$230.08	$230.10	$230.10
Purchase #3	$155.80	6.453%	$165.8538	$165.85	$165.85	$165.90
Purchase #4	$90.26	11.449%	$100.5939	$100.59	$100.60	$100.60
Purchase #5	$202.55	6.322%	$215.3552	$215.36	$215.35	$215.40
Purchase #6	$209.88	3.795%	$217.8449	$217.84	$217.85	$217.80
Purchase #7	$89.78	5.397%	$94.6254	$94.63	$94.65	$94.60
7 purchase totals =	$1,102.71		$1,165.8119	$1,165.81	$1,165.85	$1,165.90