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	$80.56	3.720%	$83.5568	$83.56	$83.55	$83.60
Purchase #2	$89.99	8.856%	$97.9595	$97.96	$97.95	$98.00
Purchase #3	$250.29	3.727%	$259.6183	$259.62	$259.60	$259.60
Purchase #4	$82.85	8.291%	$89.7191	$89.72	$89.70	$89.70
Purchase #5	$194.50	7.617%	$209.3151	$209.32	$209.30	$209.30
Purchase #6	$167.37	6.824%	$178.7913	$178.79	$178.80	$178.80
Purchase #7	$117.94	4.830%	$123.6365	$123.64	$123.65	$123.60
7 purchase totals =	$983.50		$1,042.5966	$1,042.61	$1,042.55	$1,042.60