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	$171.47	9.281%	$187.3841	$187.38	$187.40	$187.40
Purchase #2	$90.27	13.147%	$102.1378	$102.14	$102.15	$102.10
Purchase #3	$132.39	6.850%	$141.4587	$141.46	$141.45	$141.50
Purchase #4	$42.27	10.849%	$46.8559	$46.86	$46.85	$46.90
Purchase #5	$38.58	9.693%	$42.3196	$42.32	$42.30	$42.30
Purchase #6	$195.62	11.458%	$218.0341	$218.03	$218.05	$218.00
Purchase #7	$224.54	7.463%	$241.2974	$241.30	$241.30	$241.30
7 purchase totals =	$895.14		$979.4876	$979.49	$979.50	$979.50