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	$77.47	12.349%	$87.0368	$87.04	$87.05	$87.00
Purchase #2	$22.63	11.691%	$25.2757	$25.28	$25.30	$25.30
Purchase #3	$38.39	5.674%	$40.5682	$40.57	$40.55	$40.60
Purchase #4	$70.90	13.541%	$80.5006	$80.50	$80.50	$80.50
Purchase #5	$82.74	4.814%	$86.7231	$86.72	$86.70	$86.70
Purchase #6	$19.73	6.495%	$21.0115	$21.01	$21.00	$21.00
Purchase #7	$40.43	7.603%	$43.5039	$43.50	$43.50	$43.50
7 purchase totals =	$352.29		$384.6198	$384.62	$384.60	$384.60