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	$240.71	6.515%	$256.3923	$256.39	$256.40	$256.40
Purchase #2	$58.95	9.769%	$64.7088	$64.71	$64.70	$64.70
Purchase #3	$102.62	8.873%	$111.7255	$111.73	$111.75	$111.70
Purchase #4	$130.58	3.336%	$134.9361	$134.94	$134.95	$134.90
Purchase #5	$147.57	7.359%	$158.4297	$158.43	$158.45	$158.40
Purchase #6	$177.65	10.689%	$196.639	$196.64	$196.65	$196.60
Purchase #7	$96.35	13.842%	$109.6868	$109.69	$109.70	$109.70
7 purchase totals =	$954.43		$1,032.5182	$1,032.53	$1,032.60	$1,032.40