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	$53.31	13.442%	$60.4759	$60.48	$60.50	$60.50
Purchase #2	$176.98	7.859%	$190.8889	$190.89	$190.90	$190.90
Purchase #3	$116.52	6.292%	$123.8514	$123.85	$123.85	$123.90
Purchase #4	$181.83	7.766%	$195.9509	$195.95	$195.95	$196.00
Purchase #5	$205.96	4.722%	$215.6854	$215.69	$215.70	$215.70
Purchase #6	$240.67	13.231%	$272.513	$272.51	$272.50	$272.50
Purchase #7	$78.99	7.528%	$84.9364	$84.94	$84.95	$84.90
7 purchase totals =	$1,054.26		$1,144.3019	$1,144.31	$1,144.35	$1,144.40