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	$244.94	12.823%	$276.3487	$276.35	$276.35	$276.30
Purchase #2	$70.38	13.849%	$80.1269	$80.13	$80.15	$80.10
Purchase #3	$131.85	3.508%	$136.4753	$136.48	$136.50	$136.50
Purchase #4	$167.31	4.184%	$174.3103	$174.31	$174.30	$174.30
Purchase #5	$175.26	6.462%	$186.5853	$186.59	$186.60	$186.60
Purchase #6	$36.25	5.498%	$38.243	$38.24	$38.25	$38.20
Purchase #7	$247.72	3.705%	$256.898	$256.90	$256.90	$256.90
7 purchase totals =	$1,073.71		$1,148.9875	$1,149.00	$1,149.05	$1,148.90