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	$245.92	4.787%	$257.6922	$257.69	$257.70	$257.70
Purchase #2	$236.28	11.264%	$262.8946	$262.89	$262.90	$262.90
Purchase #3	$80.68	11.661%	$90.0881	$90.09	$90.10	$90.10
Purchase #4	$52.61	5.251%	$55.3726	$55.37	$55.35	$55.40
Purchase #5	$215.32	4.221%	$224.4087	$224.41	$224.40	$224.40
Purchase #6	$127.69	12.336%	$143.4418	$143.44	$143.45	$143.40
Purchase #7	$168.40	7.769%	$181.483	$181.48	$181.50	$181.50
7 purchase totals =	$1,126.90		$1,215.3810	$1,215.37	$1,215.40	$1,215.40