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	$189.75	3.518%	$196.4254	$196.43	$196.45	$196.40
Purchase #2	$174.42	9.204%	$190.4736	$190.47	$190.45	$190.50
Purchase #3	$38.50	12.396%	$43.2725	$43.27	$43.25	$43.30
Purchase #4	$113.87	3.738%	$118.1265	$118.13	$118.15	$118.10
Purchase #5	$9.62	10.528%	$10.6328	$10.63	$10.65	$10.60
Purchase #6	$24.36	4.555%	$25.4696	$25.47	$25.45	$25.50
Purchase #7	$66.41	9.849%	$72.9507	$72.95	$72.95	$73.00
7 purchase totals =	$616.93		$657.3511	$657.35	$657.35	$657.40