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	$142.62	7.554%	$153.3935	$153.39	$153.40	$153.40
Purchase #2	$126.80	7.352%	$136.1223	$136.12	$136.10	$136.10
Purchase #3	$80.45	4.204%	$83.8321	$83.83	$83.85	$83.80
Purchase #4	$161.32	4.388%	$168.3987	$168.40	$168.40	$168.40
Purchase #5	$233.62	3.804%	$242.5069	$242.51	$242.50	$242.50
Purchase #6	$60.88	3.243%	$62.8543	$62.85	$62.85	$62.90
Purchase #7	$72.78	12.169%	$81.6366	$81.64	$81.65	$81.60
7 purchase totals =	$878.47		$928.7444	$928.74	$928.75	$928.70