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	$204.91	13.402%	$232.372	$232.37	$232.35	$232.40
Purchase #2	$199.85	4.796%	$209.4348	$209.43	$209.45	$209.40
Purchase #3	$179.75	5.604%	$189.8232	$189.82	$189.80	$189.80
Purchase #4	$41.75	4.865%	$43.7811	$43.78	$43.80	$43.80
Purchase #5	$70.60	8.527%	$76.6201	$76.62	$76.60	$76.60
Purchase #6	$54.46	12.649%	$61.3486	$61.35	$61.35	$61.30
Purchase #7	$118.51	7.457%	$127.3473	$127.35	$127.35	$127.30
7 purchase totals =	$869.83		$940.7271	$940.72	$940.70	$940.60