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	$241.42	9.170%	$263.5582	$263.56	$263.55	$263.60
Purchase #2	$25.54	12.369%	$28.699	$28.70	$28.70	$28.70
Purchase #3	$123.48	10.547%	$136.5034	$136.50	$136.50	$136.50
Purchase #4	$62.59	7.517%	$67.2949	$67.29	$67.30	$67.30
Purchase #5	$193.64	11.463%	$215.837	$215.84	$215.85	$215.80
Purchase #6	$22.48	10.743%	$24.895	$24.90	$24.90	$24.90
Purchase #7	$214.30	12.781%	$241.6897	$241.69	$241.70	$241.70
7 purchase totals =	$883.45		$978.4772	$978.48	$978.50	$978.50