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	$159.86	10.436%	$176.543	$176.54	$176.55	$176.50
Purchase #2	$65.75	11.667%	$73.4211	$73.42	$73.40	$73.40
Purchase #3	$37.87	4.705%	$39.6518	$39.65	$39.65	$39.70
Purchase #4	$87.40	3.235%	$90.2274	$90.23	$90.25	$90.20
Purchase #5	$102.49	13.710%	$116.5414	$116.54	$116.55	$116.50
Purchase #6	$165.80	11.492%	$184.8537	$184.85	$184.85	$184.90
Purchase #7	$186.42	7.450%	$200.3083	$200.31	$200.30	$200.30
7 purchase totals =	$805.59		$881.5467	$881.54	$881.55	$881.50