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	$137.27	10.217%	$151.2949	$151.29	$151.30	$151.30
Purchase #2	$200.73	13.745%	$228.3203	$228.32	$228.30	$228.30
Purchase #3	$169.51	7.211%	$181.7334	$181.73	$181.75	$181.70
Purchase #4	$156.87	3.602%	$162.5205	$162.52	$162.50	$162.50
Purchase #5	$34.35	7.666%	$36.9833	$36.98	$37.00	$37.00
Purchase #6	$128.75	6.809%	$137.5166	$137.52	$137.50	$137.50
Purchase #7	$111.75	4.858%	$117.1788	$117.18	$117.20	$117.20
7 purchase totals =	$939.23		$1,015.5478	$1,015.54	$1,015.55	$1,015.50