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	$56.31	6.292%	$59.853	$59.85	$59.85	$59.90
Purchase #2	$214.94	9.805%	$236.0149	$236.01	$236.00	$236.00
Purchase #3	$52.86	5.771%	$55.9106	$55.91	$55.90	$55.90
Purchase #4	$240.26	9.176%	$262.3063	$262.31	$262.30	$262.30
Purchase #5	$123.90	12.823%	$139.7877	$139.79	$139.80	$139.80
Purchase #6	$199.68	13.617%	$226.8704	$226.87	$226.85	$226.90
Purchase #7	$54.32	12.293%	$60.9976	$61.00	$61.00	$61.00
7 purchase totals =	$942.27		$1,041.7405	$1,041.74	$1,041.70	$1,041.80