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	$241.71	5.730%	$255.56	$255.56	$255.55	$255.60
Purchase #2	$85.68	3.734%	$88.8793	$88.88	$88.90	$88.90
Purchase #3	$239.30	6.790%	$255.5485	$255.55	$255.55	$255.50
Purchase #4	$131.54	10.505%	$145.3583	$145.36	$145.35	$145.40
Purchase #5	$160.72	10.807%	$178.089	$178.09	$178.10	$178.10
Purchase #6	$85.58	3.493%	$88.5693	$88.57	$88.55	$88.60
Purchase #7	$232.32	10.431%	$256.5533	$256.55	$256.55	$256.60
7 purchase totals =	$1,176.85		$1,268.5577	$1,268.56	$1,268.55	$1,268.70