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	$63.83	13.664%	$72.5517	$72.55	$72.55	$72.60
Purchase #2	$172.64	9.775%	$189.5156	$189.52	$189.50	$189.50
Purchase #3	$118.69	8.607%	$128.9056	$128.91	$128.90	$128.90
Purchase #4	$242.99	12.116%	$272.4307	$272.43	$272.45	$272.40
Purchase #5	$138.61	13.261%	$156.9911	$156.99	$157.00	$157.00
Purchase #6	$185.83	5.236%	$195.5601	$195.56	$195.55	$195.60
Purchase #7	$74.54	10.477%	$82.3496	$82.35	$82.35	$82.30
7 purchase totals =	$997.13		$1,098.3044	$1,098.31	$1,098.30	$1,098.30