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	$187.56	13.707%	$213.2688	$213.27	$213.25	$213.30
Purchase #2	$176.52	13.818%	$200.9115	$200.91	$200.90	$200.90
Purchase #3	$194.66	6.763%	$207.8249	$207.82	$207.80	$207.80
Purchase #4	$74.36	8.334%	$80.5572	$80.56	$80.55	$80.60
Purchase #5	$21.92	4.508%	$22.9082	$22.91	$22.90	$22.90
Purchase #6	$107.83	3.487%	$111.59	$111.59	$111.60	$111.60
Purchase #7	$219.26	9.253%	$239.5481	$239.55	$239.55	$239.50
7 purchase totals =	$982.11		$1,076.6087	$1,076.61	$1,076.55	$1,076.60